The F is capitalized. He did NOT capitalize his F.
How many must I have to point to the fact that what you think is a capital F is a lower case f.
Look closely, the line gores through the line on it as it does in a lower case f.
A capital F does not have the line going through. Do not get confused with the size of the letters. They often times offer a lower case letter that is much larger than an upper case letter in the same captcha. Size matters not.