width parameter for SbSmooth?

The help for sub-band smoother is confusing - could someone please clarify?

The module supports two different forms of smoothing. In linear smoothing (type = 0), N bins to the left and N bins to the right of each bin are averaged, where N is a fixed number. The number of bins N is specified by the parameter .width, and .width is specified in Hz. If a bin is centered at frequency F, then the bins in the range [F-width F+width] are averaged.

Which is it? Is width "the number of bins N" (an integer)?  or is it a frequency range ("specified in Hz")?

Thanks!