Looks like the legend is offset by one bucket.
The API returns the upper bounds of a bucket. So the first bucket value in the legend should read "under xx" and the top end would read "yy-zz" instead of "zz and over".
Actually, looking at this closer it seems as if a bin value may be missing in the values the api is returning, but the fix may still require some client side changes.
Looks like the legend is offset by one bucket. The API returns the upper bounds of a bucket. So the first bucket value in the legend should read "under xx" and the top end would read "yy-zz" instead of "zz and over".