When does time supply capped count?

Solution 1:

This is great explanation from RhokenStrolm

"Supply Capped" is where you are trying to build a unit but can't because you don't have enough supply.

And about 200/200...

It doesn't measure 200/200. It measures when you are supply blocked and stops when you build a pylon/depot/overlord.

Source.

Solution 2:

It doesn't measure if you are at 200/200.

The goal of the statistic is so you can see how many seconds you wasted not being able to produce units due to lack of supply depots,and since supply depots can't increase your capacity over 200 the timer stops telling you it isn't your fault anymore.

Interesting question would be if it counts when you are at 49/50 since it isn't maxed but you can't make any useful unit...As far as i know it doesn't count that either.