How to specify the unit in formatted output

[rdiez]

I want to monitor the upload and download bandwidths, so I am using a command like this:

$ bmon --policy=wlp5s0 --use-si --output format:fmt='$(element:name)\t$(attr:rxrate:bytes)\t$(attr:txrate:bytes)\n'

wlp5s0 0.00 0.00
wlp5s0 53.99 81.99
wlp5s0 363.75 798.25

I do not know what units the values are in. How do I specify the unit anyway? For example, I would like to use kBytes/s.