Numbers
The number 6 in braille
6 is the number sign followed by the letter f — dots 1, 2 and 4.
Number sign + f
Dots 3-4-5-6, then dots 1-2-4
Why it uses a letter
The first ten letters of the alphabet double as the ten digits. f is letter 6 of the alphabet, so after a number sign it reads as 6. Without the number sign the same cell is simply the letter f — see F in braille.
6 inside larger numbers
A number sign covers the whole run of digits that follows it, so these examples each use one indicator regardless of length.
6
16
600