please see attached spreadsheet
please see attached spreadsheet
The error in your formula is in setting the match type. For an exact match the type should be 0 (zero), like =MATCH(A6,$G$6:$G$23,0).
However, if your worksheet is constructed like the one you published, using VLOOKUP would be the better solution because it's simpler and, therefore, works faster.
=IFERROR(VLOOKUP($A6,$G$6:$H$23,2,FALSE),0)
Bear in mind that the lookup column must be the first column in the specified range, with the result column anywhere to the right of it.