Wrong forum.
The maximum speed of a cable modem is 50 Mbps or so, minimal is 0 of course, so that makes an average of 25 Mbps. If you're not capped.
Considering your speed I'd say you're capped at 3 Mbps. You're at 90% of your advertised speed already, so it's great already. But if you want to tweak, go ahead and get faster. The 3 day average on testmy.net is about 1.3 Mbps, you're way above that.
Beware that you'll be placed on the list if you go over 3 Mbps.