Ok, so I ran a speedtes with my ISP and with Speedtest.net, here are the results below:
The download speeds are close to each other, and Xfinity says that my peak upload is over 3Mb/s, whereas speedtest showed my current upload speed.
All in all, according to Xfinity my speeds should be: 2,300Kb/s DL and ~300Kb/s UL.