This setting is used if the user needs to change the voucher expiry date that is set to 6 months by default.
This is all configured from the POS:
- From Advanced > Company Settings > More > Vouchers section
Advanced
Company settings
In the More tab, press amend button and increase or decrease the number of days from the arrows.

Because this is a Company Setting, after you set up your Default Expiry Days is best if you log out and then in into the POS so the settings will be applied.