Jesse, check the units -- it probably does make sense. The speed tests return values in kpbs (kiloBITS per second), but most downloads are measured in KB/s (kiloBYTES per second). There are 8 bits in a byte plus add 1 stop bit for transmission, so divide by 9 for a rough translation. 755 kbps comes out to 84 KB/s (755 รท 9). So 90 KB/s is very close to 84 and that makes perfect sense.
The next question would be: are you getting what you paid for? What tier of service are you getting from CenturyTel? Based on the test results, it looks like 768 kbps downstream and 256 kbps upstream (sometimes written 768/256). If that's what you are paying for, you are getting it. However, if you are paying for up to 1.5 Mpbs, it's a little slow. Beware of the "up to" clause, but if you are not getting close to what you paid for give them a call and ask if they can fix it.