Square
Box, Measure
noun
Measure that shape on the paper with your eyes. It's got four sides.. it's.. it's a square! Or a box from above maybe... But it's definitely the kind you fill in on a graph.
ますめ
The readings for this word are both kun'yomi readings. You learned them when you learned the kanji, so you should be able to read this on your own.
升目を数えると、全部で400ありました。
When I counted the boxes there were 400 total.