What does it mean the exercise says that you should "contract" your abs at the top of the movement? Does it imply that you should squeeze out as if you were trying to puff your stomach out? Or does it mean that you should squeeze in as if you were trying to suck in your gut? This has always confused me.

Squeeze to make the muscle tight (like you were trying to suck it in or as in the crunch type movement).

Okay, thanks. I think I've been doing it wrong. I've been pushing out. Like squeezing it upwards or pushing towards the air not sucking it in and squeezing it as if I was trying to push it through my back. Perhaps not the best choice of words but that's about how I'd describe it.

Despite the fact that my stomach is very lean and you can see definition, my pants which were loose a year or two ago are now exceptionally tight and I think it's because I've been doing the exercises wrong.