Comcast broadband is baffling

My Comcast cable modem is fast - I get about 6mbps down and about 300kbps up, which is usually bout 45 kib/sec upload. I used to pay a $10 premium to bump that upload to about 60 or 90 kib/sec.

For some reason today I'm getting speeds at close to 300kib/sec upload on compressed files (i.e. I'm not enjoying escalated speed because of modem compression or other tricks). That's over 600% of the speed I bought.

I don't get it. Is the cap broken? Have they bumped the speed all basic accounts?