Hey,

I have a armortec 800 def.
It is strung 23lbs cross, 21lbs main

Does this mean my string tension is 22lbs?

Depends. Some people say it's "21lbs." Other say it's "23lbs."

I say it's "21/23lbs." :p

I'd say it is 23 pounds. If people ask me to string for 26 pounds, I would give them 24 mains and 26 cross. I am not a professional stringer but I have no complaints about my tensions yet.

It's usually better to clearly specify the main and cross tension separately. Otherwise, it's down to the stringer to make the decision. This is also another reason why try to stick with one stringer, if you like service. This way, s/he exactly knows what you need. ;)