Probably are the positions and sizes of the QR code image (4 values)... and the other 3 dunno... probably the text that is displayed with it (remember text objects have the standard position, size, and other value for the font size of something like that, not sure if is still marked as unknown in the "rcomage psdevwiki mod")
The problem of what you are suggesting (taking the layout.txt files from 4.88 to use them in 4.89) is with them you are going to need to copy all the rco files from 4.88 too
Is a bit tricky to explain, but you know how it works... the "rcoxml objects" inside the rco files contains tenths of values that are a reference to load the real values from the layout.txt files
The layout.txt files from 4.88 contains 4595 lines (all the values loaded by the complete rco collection from 4.88). And the new 7 values added are located at line 2580
This means all the values located after line 2580 has been displaced... so all the rcos ffrom 4.89 that loads values from lines bigger than 2580 are not going to be able to find the value in the layout.txt from 4.88
The real problem is we dont have a list of who is the "owner" of each value inside the layout.txt files... so we dont know how many rco files are going to be broken if you use the layout.txt from 4.88 in 4.89
Dunno, im still thinking in it but i dont see any easy solution by now
EDIT:
I just updated this wiki page, if there is some other info worthy to be added tell me
https://www.psdevwiki.com/ps3/XMB_Layouts