For wintertime, possibly you'll be ok, although it is none too excessive for 4 chickens in a 4x4 coop, esp. if you have to shut the vents atop one of the walls due to wind.
For summertime, I dunno... are those two windows I see on the two sides? If they are, and those plus the vents atop the front and back walls will be open basically all the time, it is probably sufficient for a mild-summer climate or a partly-to-mostly-shaded location. If you are somewhere that gets Hot Summers, you'd be better off with more.
JMHO, good luck, have fun,
Pat