"FFFFFFFF'S!!!" joke

Quickly read through the following text and count the number of F's in it.
FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS
Managed it?
Scroll down only after you have counted them!
>
>>
>>>
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
OK?
How many?
Three?
Wrong, there are six - no joke! Read again!
FINISHED FILES ARE THE RESULT OF YEARS OF SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCE OF YEARS
The reasoning is that the brain cannot process the word "OF".
Incredible or what?
Anyone who counts all six F's on the first go is a genius. Three is normal.