Enter the following array formula

=MAX(IF(LEFT($A$2:$A$12,1)=$C2,RIGHT($A$2:$A$12,3)*1))

Edit the array formula

Click the cell containing the the cell containing the array formula.

Click the edit bar

. When the edit field is active, the parentheses ({ }) do not appear in the array formula.

Edit the contents of the array formula.

Press Ctrl+Shift+Enter.