Miscount
/ˌmɪsˈkaʊnt/
Definition 1 of 1
Pro Tip 1/3Easy Mistake
Miscounting often happens with similar looking items or numbers, leading to an easy error. 
During the inventory, I miscounted the number of black socks as they looked like the navy ones.
Pro Tip 2/3Checking Twice
Always verify your count to avoid mistakes, especially when dealing with important items. 
I miscounted the attendees first, but checking again I realized the error.
Pro Tip 3/3High Stakes
A miscount can have significant consequences in formal and official matters like elections or finances. 
The election had to be recounted after they miscounted the ballots.