Newbie: problem understanding Polar fitness test

diverdiza

Hi all. Brand new to the site - only found it last night. I hope the good folks here can help more than the Polar forum - I think there are a lot more people here that's for sure!
I have a Polar F11 which I've had for a number of years.
I've never managed to really get to grips with the fitness test.
If I set it with "low" activity level then the fitness test puts me at between 16 and 20 - VERY LOW. If I change the setting to "moderate" then my test results are high 40's to early 50s - ELITE!
Now I know I am pretty unfit so the "elite" is definitely not correct but:
(a) I don't get how such a simple setting would change the outcome THAT MUCH and
(b) even if I accept the "very low" reading I don't seem to make any progress - my resting HR seems to be coming down and I can certainly exercise harder than before but my tests basically come back almost identical - in fact the most recent one shows I have gone backwards!

I'd really appreciate some insight.....
Thanks in advance!