So you have 5 signs in the tunnels and the code on the wall indicates only 3.
Look at the symbols and match the same symbol per row. After that you count the spots where the same symbols are (per row).
So these match:
Symbol 2 and symbol 6 are the same: Bone Orchard Vein
Symbol 2 and symbol 8 are the same: Lunger Undermines
Symbol 2 and symbol 10 are the same: Consumption Cross
Symbol 2 and symbol 11 are the same: Dry Gulcher Shaft
Symbol 2 and symbol 12 are the same: Ground Biter Pits
Another way is to notice what the space-symbol looks like and count the place where the spaces are, this way is faster then any other tho.
GL & HF!