Illustrator scaling from transform window not working properly

[dimonsolian]

So, I've been going crazy about this problem. Basically, when I try to scale any object from the transform window by introducing a number manually, say for example 30mm, Illustrator will change it to, say, 29,87mm for the hight and 29,738mm for width. Mind you, I'm talking about a square, that I created with the shape tool, so when created it was actually square and not off by a few mm.
I'd also like to add that sometimes when alligning or snapping, I find that it's also off by a few pixels, and sometimes I can't really get it to align properly.
Has anyone else encountered this issue/bug? Any solutions?
For version 25.4.1

[manal shanableh]

have you tried to remove maintain width and height proportions??

[Met1]

Got a stroke on your box?

You can include or exclude the stroke from measurements.

Check (or uncheck) Use Preview Bounds in prefs.

[Monika Gause]

As for the snapping: If align to pixels is turned on, then you might get into trouble.

[Anshul_Saini]

Hi there,

Sorry about the trouble. I would like to know if the steps suggested above worked for you? If not, I would request you to share a few more details like:

• Operating System
• Is the issue related to a specific document?
• Could you please share a sample document with us? You can upload it to the Creative Cloud (https://helpx.adobe.com/in/creative-cloud/help/share.html) and share the download link.
• When did this start happening? Are there any recent changes made to your system? For example, any antivirus, system updates, plugins, or web extensions installed recently.
• A small video of your workflow from the start demonstrating the issue could be really helpful.
• Does resetting Illustrator Preferences ( https://helpx.adobe.com/illustrator/using/setting-preferences.html) help to resolve the issue?
  Disclaimer: Please note that resetting preferences will remove all the custom settings, and Illustrator will launch with default settings. You can also take a backup of the folders in case you want to. Location is mentioned in the article.

We will be looking forward to your response.

Thanks & Regards,

Anshul Saini

[Enlightened_play5CFB]

Hi, 

I'm not sure if this is exactly the same issue, but I keep having trouble to work with even numbers in illustrator. Quiet often it jumps ro unwated/randome fractions/decimals. That happens if I try to draw geometric shapes, position them or scaling them. To explain and illustrate, let me focus on one scenario here. 
Let's say I draw a perfect circle. I now want to round the numbers, in this example from 447.3015 px square to 400.00 px square. With "Constrain Witdh and Height Proportions" still selected I type in 400 px Width. I'm getting 400 px width but 399.7687 px height. Why not 400 px by 400 px?!
See screenshots below.

[Monika Gause]

Is there a stroke applied to the object?

Is any snapping active?

[Enlightened_play5CFB]

Hi Monika, 

The circle has a 2px stroke; no snapping active (as far as I'm aware).

[Enlightened_play5CFB]

Scale strokes and effects is off

[Monika Gause]

Please check the snapping options in the View menu.

Does it work without the stroke?

[Enlightened_play5CFB]

As per my screenshot of the View menu in my previous post, all snapping options are off (except Smart Guides is checked on, but I don't have any guides on this document) – do you want me to turn snappings on?
Without the stroke it seems to work fine – why is that (doesn't seem to make sense to me); does that mean I can't work with shapes that have strokes/outlines?

[Ton Frederiks]

Is Use Preview Bounds checked in the Preferences (or the Align Panel)?

[Enlightened_play5CFB · Accepted solution]

Use Preview Bounds was checked in the Align Panel – I made sure it's checked off in both places.
And voila. It now gives me squared/straight numbers, even with strokes and outlined obejcts. 
Monika and Frederik: Thank you both for the quick support, and for helping me solve the issue! I really appreciate that!

[Ton Frederiks]

Good to hear that helped.