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.
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.