Formula not working inside another formula?

Pease Help me to get this work

$tc(len, "mi(title)")$ always gives a 9.

I mean it's correct but you know what I want. Please help me.

When you use a code inside a formula you need to erase the quotation marks, if not the formula are going to take the words inside it literally, like in your formula, it's always counting mi(title) =9

try with