What is the number of balanced strings of 5 left and 5 right brackets whichend with RR?

The answer is 42-14 = 28 ...

I know 42 is the number of ways we can arrange 5 balacned strings of brackets... but why did we pick the number 14 which is the number of ways to arrange 4 balanced strings of brackets...

can some one clear this one for me thanks