It's the first 20 days, but it's actually for anything you do. HughesNet gives it for the primary purpose of letting you update or upgrade without burning through your data, but you can use it for anything. Some people go on streaming or other downloading sprees. 
The 20GB plan has always been enough for me during normal activities, but I did exhaust my data for the first time a couple of months ago, and I'll do it again this month. Good ole PlayOn Cloud is the reason. I was too tired to wait up to download the files during the Bonus Zone, and too lazy to schedule the downloads to my phone. It was only about 7GB, but that was enough. So, as of right now, I have ten days left in my data cycle, but only 1.4GB of data. I still have plenty of Bonus Zone data, but that's not going to help me during the day. Luckily, though, I have a good amount of Token data, so I won't actually go into FAP.
If you go into FAP (Fair Access Policy (i.e. exhausting your data)), I hope that you do get between 1Mbps and 3Mbps. I think most people do.
Regarding ExSat, I think he's strictly wireless now, having gotten in on the Verizon prepaid data thing before they ended it for new sign ups.
