The purpose of modifying your barcodes and stripping out certain characters is mainly to make them easier to find and see in management.
For example, you may receive some resources from your SLS with preassigned barcodes, these barcodes could be upwards of 10 digits long, and many of the characters in the barcode are the same for every resource making them unnecessary when searching for the book. You can use a barcode mask to strip this unneeded characters, so that only the unique characters show when looking in management, making them neater and easier to find.