sorry for the long title but i recently bought my first half stack and the ohm thing is a little confusing to me.

i set it to mono and i guess i have to put my speaker cable in the closest "hole" but above the hole there's 4 ohm (input) and on the left of the hole there's 8 ohm (right)

however, on the head there are 5 inputs
-1 4
-2 8
-1 8
-2 16
-1 16

if i think logical the ones with a 2 are for stereo and i don't need that but as said before, i now nothing of this subject.
help would be apreciated
Just match to the cab either 4, 8 or 16 mono. If you are not sure on your cabinets ohm rating you can either look it up, or better yet stick a multimeter pos and neg tips on the end of the speaker cable that normally plugs into amp. Set multimeter for 20 mA. Then you will know for sure.