Help Calculating a percentage

I am hoping somebody can point me in the right direction regarding a spreadsheet I have recently half finished

I have attached it below.

The "letter" data is produced using the Concatenate formula, and Left, Mid, Right etc.

I thought it would be quite elementary to calculate percentages, how wrong I was!

What I want to do is calculate the % of say two capital "F"s , or two capital "F"s and one capital "M" out of the 64 total cells.

I hope I have explained that correctly, I know what I mean, but not sure I have explained it very well.

Thanks in advance.