Can You Help Explain These Resaults?

[FlyingFish]

Hi There,

Just got a 5 in 1 test.

Here's the resaults:
nitrate 0-10mg/l
nitrite 0-1mg/l
General hardness >10*d
carbonate 3*d
PH 7.2 - 7.6

can you help me explain these? are the levels ok?
Have a 12G tank with 4 black widow tetras

 

[WILDER]

A slight nitrite readings there, i would preform a water change, everything else looks fine, black window tetras need to be in a bigger tank, that tank is to small you need a least a 20gal for them, how many fish do you have in the tank, and which kind, plus what filter are you using.