I misread the requirement, most probably.
Which result is accurate
abc1da1f ---> a1a1a1a1a1a = 1 (matching single max case)
I thought third as requirement. Here's a formula which will give you maximum match number which needs to be entered by CSE.
=MAX(IF(ISNUMBER(FIND(MID(B2,COLUMN($A$1:INDEX($1:$1,LEN(B2))),ROW($A$1:INDEX($A:$A,LEN(B2)))),A2))*ISNUMBER(--MID(B2,COLUMN($A$1:INDEX($1:$1,LEN(B2))),ROW($A$1:INDEX($A:$A,LEN(B2))))),--MID(B2,COLUMN($A$1:INDEX($1:$1,LEN(B2))),ROW($A$1:INDEX($A:$A,LEN(B2)))),0))