Often a larger and thicker wallet indicates a man with greater wealth and social status (a hoe lotta benjamins in dar). Women are attracted to men with fat wallets. Works better than pheromones. I've long desired to be a "8 up Wallet" guy.
This may help you. I hope this sheds some light for you.
The 2-up, 4-up, etc is from printing terminology, and has significance. Please See:
In photography, especially since digital is here, folks do their own printing so new terminology is used and is really not a true definition of the process. It stretches things a bit.
Many photo and other printer companies offer software with their printers that can print multiple pictures per sheet. Adobe Photoshop has an "automate" feature where one can select predetermined sizes per sheet. And there are more sophisticated printing programs such as "Qimage" where one can designate the CUSTOM sizes wanted ort select for a pre sized category -- and one can even set the size of paper that will be used.
Wallet size has also changed, it used to be 2-1/8 x 3-3/8, now it seems the credit card size has now been adopted.
Sowhen you go to print "wallet size" dimensions in some printing programs you will not get multiples of 2. It depends upon the software of the printing program, or how one can make most use of the size of the sheet for printing. Now the most standard printing sheet for general type printing is the letter size of 8-1/2 x 11 inches. So with this you will see that you will probably get an array of 3 x 3 or 9 photos per sheet. I suppose you could cut sheets to smaller size to acommodate a smaller amount per page.
Most photo printers do not print on sheets, they print on rolls and therefore the only cutting is to separate each photo.
Whereas, when printing multiple photos on one sheet, the cutting has to be done to separate all of the photos. In this instance, the cutter would depend upon the number of photos printed.
If I remember correctly... wallets are 1/2 of a standard 3 1/2 x 5 inch print, or 3 1/2 x 2 1/2. This was the easiest way to print them on a mini-lab. A 4-up would be 4 on a 5x7 inch print, as most mini-labs used 5 inch paper on a roll that was advanced to the length needed. An 8-up would be 8 wallets on 8x10 paper with a little waste on the width (2 rows of 4 @ 3 1/2 x 10).