Using your posted workbook
and
I2: CHALLENGER 350
I3: CHALLENGER 360
This regular formula returns the count of unique values prefixed by the referenced cell:
H2: =SUMPRODUCT(ISNUMBER(--TRIM(SUBSTITUTE(UPPER($C$3:$C$50),UPPER(I4),"")))*($C$3:$C$50<>""),
--(MATCH($C$3:$C$50&"",$C$3:$C$50&"",0)=ROW($C$3:$C$50)-2))
Copy that formula into H3

For your data, those formulas return:
16 <-I think your count was off by one
6

Note: that formula works as long as the last characters are numeric.

Is that something you can work with?