overcount1
/ˈəʊvəkaʊnt/noun
Overcounting; an enumeration or estimate which is erroneously high.
Origin
1920s. From overcount. Compare earlier overcounting.
overcount2
/ˌəʊvəˈkaʊnt/verb
[with object] To arrive at an erroneously high total when counting (something); to overestimate.
Origin
Late 16th century; earliest use found in Joshua Sylvester (d. 1618), poet and translator. From over- + count.