Hover label incorrect when number is very small (or large?)

[rreusser]

Live example: http://codepen.io/rsreusser/pen/JKLGOL?editors=0010
(change min, max to see effect on when labels displayed correctly. I haven't figured out the pattern yet.)

Expected behavior: very small values show a hover label that represents the value. Shows scientific notation if beyond meaningful suffixes.

Observed behavior: Depending on the overall magnitudes involved, SI suffixes often just go missing. Which wouldn't be a big deal except for the fact that 1 when it should read 1n is actually incorrect.

See SI prefixes here: http://www.npl.co.uk/reference/measurement-units/si-prefixes/