One of the weirdest bugs/glitches I've ever seen... jpg file size.

I received 3 files from an agency in layers. Relatively medium in size, about 34 megs each.  If I flatten them and save as jpgs, they are ALWAYS 24 megs.  I've changed image size to 1"x1" at 72 dpi and every size in between and they are always 24 megs.

I had a coworker try it on his desktop, our server, same exact result.  We even tried making a new document, flattening the problematic file and dragging it in and saving it - same result 24 megs. 

Even tried saving as a different format png - same thing!  

Both of us have never seen this in 20 years of using Photoshop. We have checked color settings and profile, color mode, bit depth, channels, layers, etc. nothing works.

Anyone else experience this?  By far, the strangest thing I've encountered.