Yes

You think about the clue and try to think about what is presented to you. The only exposed parts of these bound twinks are their asses, which stored the keys, and their cocks. Their cocks... could it really be that? The hint did mention length... but there was two problems. The first was that you didn’t have a ruler. The second was that the majority of the cocks were soft, and you figured if it was length it would be the full amount.

Going with this hunch, you go to the boy who had the first fitting key, and start to quickly stroke him. You lick your palms as he moans at the sudden ****, bound to not be able to resist. Very quickly, he gets to what you figure is his full length.

Thinking for a second, you realize you know the length of your own cock, and could compare the two. Thankfully you are already hard from all the erotic trials, and you hold up your 6 inch cock to press side to side with the newly erect cock. It seems you are about an inch longer. Smiling you start to walk away to input in the amount, when the bound boy starts moaning and jumping as much as he can in his bonds. Clearly the teased boy needs to cum, and you wonder how long he has been bound and teased without release. You could milk the poor soul, helping him out, but it would waste valuable time.