Taprite guage

I have 2 beers in the kegs each at around 40 degrees and at 10 psi they have been carbonating since wed. I coundn't resist and tapped one last night there is very little carbonation in there and I'm looking at my tap rite guage and wondering if I have it set right. Let's say I'm at 20 pounds and going to 40 theres a line for 25 a line for 30 a line for 35 then the number 40 thats 3 lines for 3 numbers but from 0 to 10 there is only 2 lines. It goes 0 line line 20 I'm at the first line is that 5 or 10 or is 5 like the minimum as soon as the regulator is turned on. I know it takes more days to carb but they were very flat.

Most regulators can run as low as 1-2 psi. The gage won't change that, but it can be hard to read. I'd guess the first line is 10 psi and the second 15, because it is quite common for gages to have a minimum pressure they can read. Try the second line and give it another week.

I had a similar problem, it took a couple of weeks for my corny to slow carb, set at 10 psi. I was told to vent the headspace, re-carb, let it sit for a few days, and repeat. This seemed to work very well. You definitely need to vent the air out of the headspace when first carbing the keg, I probably just forgot.