Yes you are only allowed to select one category, once. Hence, for tickets, if you would like 2 x $100 VIP tickets, then input $200 into the amount to be pledged. If you'd like 3 tickets, input $300. For 4 tickets, input $400.
Likewise, for the $200 VVIP tickets category, for 1 ticket, enter $200 as your pledge amount. For 2 tickets, enter $400, and so on.