The voucher redeem process is fast, not complicated, you have to arrive 15 minutes before the time slot you bought so you don't have to wait for the queue to be empty (because when we missed it and had to wait in a long queue there was an empty one to get in), unfortunately when we were on Skybridge lt. 86 or at the observation deck, 86th floor, it seems like you're being rushed/limited in time, only 15 minutes, but it's your turn at the gift & coffee shop lt. 83 even left it for a long time, didn't wait for it...