Correct. If 250 M people use it in the US out of a population of 349 M, Google would make 401 B USD out of them, vs 403 B USD in worldwide revenues. These numbers do not look right to me.
median is the sample in the middle of the distribution (when it is treated as a sequence of samples ordered by their value), e.g. if you have sort(seq(dist))=[100$, 5$, 5$, 3$, 1$] the median is 5$
average is sum(dist)/size(dist), so avg * size(dist) => sum(dist)
in the example above that would be median 5, avg. 22.8, total 114, size 5
if you where to multiple the median by size you would have 25$ for the total value, which is very much very wrong