reverse engineer software database to enable viewing and editing

We are looking for someone super smart to look at the two attached files, to figure out how they work, and how we can edit them. the two attached files are numbers-Invs and descrp-Sold these files can be opened up by a propriety software, that does not use a standard database technology. it is using a custom build it database system. I need a way to be able to modify these files. for example one of the line items you will see the number is 5954.66 and I want to be able to change that number to 5900.00 if you can figure out how to make this change, and teach me how to do it, we will have reached our goal. I have tried to view these files with a hex editor, I see the description of the items, but I don't see the numbers. I do know one thing, the app works this way; numbers-Invs file contains the numbers. (5954.66 is somehow in this file, but I can not see it with the hex editor.) descrp-Sold file contains the description of the items sold, example apple. I can see this and edit it with the hex editor and that works. the challenge is finding the numbers, and modifying the numbers. when I look at these two files from the propriety software, i see everything perfect. see the attached screenshots. "Image 00*.jpg"