Seems random to me. In the upload list, it uses kB/s until it hits 4.0 MB/s. (Most people including me are not going to reach 1 GB/s so that one doesn't matter much there, but it doesn't necessarily have to be limited to MB.) Stats tab seems to use GB properly for "Overall upload" but always uses MB for "Overall upload (this run)" so far.
Also, 1024? I thought you use 1000 because I read that somewhere on the site. But anyway, if you're using 1024, you really should be using IEC binary units (KiB, MiB, GiB). <https://en.wikipedia.org/wiki/Binary_prefix> That will avoid people being confused with the OS showing different sizes than the app, because Windows uses them wrong too. (Sure, some people may ask what the hell those units are, but there's plenty of things users are too lazy to look up...) I don't mind if you stay with the current units and just change the multipler to 1000 per SI either. Or if you insist on following the common wrong usage, please at least don't use lowercase "kB" which suggests you're complying with SI standards. In that case, just use "KB" like Windows does.