I assume you have a 1-day ticket due to a package deal and cannot rebook without the 1-day ticket.
Your options are:
- Redeem the GAD voucher for the 1-day GAD ticket, upgrade that to a 6-day ticket, and pocket the 1-day ticket you already had for a future trip (best savings)
- Redeem the GAD voucher for the 1-day GAD ticket, upgrade either ticket to a 5-day ticket, and use them separately. This is a POOR value, as the difference between a 5-day and a 6-day ticket is $3+tax.
- Upgrade the existing 1-day ticket to a 6-day, and redeem the GAD voucher for one of the three alternate options.