VLOOKUP - Strange results

The following code is used to calculate a golf handicap based upon the category it falls in on the table (see file). For some reason the calculation works perfect for the code in cell C5 but when filled across the row to retrieve the same calculation I don't get the correct results!

=IF(B11="",B5,IF(B14<=0,B5-(VLOOKUP(B4,$B$22:$E$25,4,FALSE)*B14),IF(B14>4,B5+0.1,B5)))

As the Net Handicap Score in C14 is -1 the correct result in D5 should be 23.60 - 0.4 giving 23.20 for the exact handicap score, why is this?