@aspireryan
Maybe it will help you to understand if said in very basic terms with an image to illustrate the process.

Osiris means that you need to reduce the new image to be at least equal or less than the size of the existing one. Your 'Ford' bitmap is 122,052 bytes and the [shrunk] Lexus one is 120,350 bytes. When you find 'PNG' in plain text in a hex editor, it is shown as '50 4E 47' in hexadecimal, on the plain text side there will be a meaningless symbol just before PNG which is '89' in hex:

logo hex

So starting on the left of '89', count back 15 bytes [squares] then you will be at 'C4' and 'the 4 octets is size of image' means you take 'C4DC0100' and then reverse to get '0001DCC4' and that when converted to decimal will disclose the size of the previously loaded Ford image, which i find to be 122,052 bytes and that tallies with the size disclosed in the image's Windows' properties [133,337 bytes or '0208D9' coincidentally is the size of the 'lexus2.png' which you supplied so maybe that's a typo rather than one of my usual cock-ups ]. However, i do convert '0001D61E' as 120,350 bytes which is what Osiris has for the new reduced Lexus image to make it less than the original Ford one.

Of course if you're not so comfortable using a hex editor, you can easily and visually check the image size by opening the logo bin file in GIR_Editor and a tmp.png file will be saved automatically in the bin file's same directory for you to then easily check its size by right click > Properties.

An easy online hex > dec converter, there's lots of them around:
Code:
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