Thank you Teufel,
Funny how the man doesn't explain this.
It does describe the -h option:
with -l, print sizes in human readable format (e.g., 1K 234M 2G)
And give a quick blurb at the bottom but doesn't indicate that the returned "total" value was size:
SIZE may be (or may be an integer optionally followed by) one of following: KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.
Without having to ask the question, how could I have figured this out by myself?