Here is a classic example that this kind of service is free:
http://www.elfqrin.com/hacklab/pages/discard.phpBasically, every number is possible, when it is valid by checking it with some algorithms.
There a bunch of free softwares like yours to download at HF.
BTW, how would you check the validating number that is in the invoice of the card?
Lmao the link you provided that checks vcc/cc is fake. I typed random letters and it said its a credit card nor it is a valid credit card. There are plenty of useful tool online that can check / verify master,visa, cards. This also works with the vcc generator. For instance, you've generated a vcc then you can check it if its valid at: