How to change Blu-ray size

I find it interesting that people are having issues if Encrore "inflating" a Blu-ray file size. I have an issue with it DECREASING the file size. I have a 22GB HD file and when I bring it into Encore to burn a BD, it ends up being only 15GB wish so much empty disc space. 
When it comes to INFLATING a video file, I find that to happen when burning DVD in Encore. Every single DVD I have ever burned in Encore, as small as 1.5GB has burned the entire disc with no empty space left over. How and why is that? Anyone?

nilsb13505332  wrote how can I adjust the size of the Blu-ray manually so Encore doesnt inflate the file to maximum 24,9gb? thank you

You will have to export from Premiere again with a lower bitrate to make the file fit.

If your videos are not Blu-ray legal in Encore's opinion, it will show them as "Untranscoded" in the project panel under "Blu-ray Transcode Status." When this is the case, Encore will transcode/retranscode them using the settings shown in the "Transcode Settings" column. You can change the settings by picking a "quality preset" or creating a custom one.

If the setting is "automatic," Encore will use bitrates to fill the disk. The goal is always to bring Encore BD ready assets (separate files for video and audio) and at bitrates that your total project is the right size. Automatic was most useful when using dynamic link, but many users never liked that workflow. Encore did not provide the best quality.

This gets into bit budgeting:

DVD-HQ : Bitrate & GOP calculator

If your video is legal, it will show "Do Not Transcode" in the status column. In that case, as you note, you may be running into the fact that a 25GB BD disk is only 23.3 GiB. In Encore, it says it is tracking GB in the build panel, but it is really tracking GiB.

Another possibility is that an iso may be of a size that cannot be burned to disk if it were a single file, but will fit when burned as a BD image. But I think you are right; the iso is too big.