How full are your CO2 tank fills?

[SoCaler]

This is my first grow with CO2. I just hooked up my second tank and it only had 700psi in it, the one had 900psi, but the 20lb tank can hold 1800psi.
WTF is up with this! I'm doing the exchange thing, and haven't asked my hydro place yet, I wanted to hear from some of the much more experience than me if this is common or what.
:sign0065:

 

[~xO Kakalak Ox~]

They don't go by PSI when they fill them. They hang the tank on a scale to fill it and stop when it weighs 20 pounds more. Thats why they call em 20 pound tanks.