Ok, really really no0b question here (as I mentioned before, I'm more familiar with ODI than test cricket):

At the top of the match scorecard, it often (not right now, because we've surpassed it) mentions a "minimum overs remaining" or something along those lines?

What's that all about? Minimum overs until what? I've never encountered mention of a minimum number of overs per innings in test cricket anywhere else...?