Captive Portal customize vouchers system

[waqaralisofi]

My clients are facing difficulties when trying to log in using the vouchers I provide. The current voucher format is somewhat complicated for them. Here's the current format as an example:

Voucher Format:
Username: Gj54
Password: vxTd4

I'm interested in simplifying this format, perhaps by using just a voucher number or even by combining the username and password into a single numeric code. Is it feasible to use only numeric codes for authentication? Your input on this matter would be greatly appreciated.