Add note to the granularity options

[petrvecera]

Summary of changes

We were really confused by the singular and plural version. I asked couple of my colleagues and they didn't know the different either. The truth has been mind blowing we didn't count with 😄

Checklist

• New functions have typespecs, changed functions were updated
• Same for documentation, including moduledocs
• Tests were added or updated to cover changes
• Commits were squashed into a single coherent commit
• Notes added to CHANGELOG file which describe changes at a high-level

[coveralls]

Coverage decreased (-0.08%) to 71.987% when pulling 6576fb4 on petrvecera:patch-1 into 78bee8d on bitwalker:master.

[coveralls]

Coverage increased (+0.3%) to 72.41% when pulling 6576fb4 on petrvecera:patch-1 into 78bee8d on bitwalker:master.