Insensitive? I'm not sure editor counted (8)
I believe the answer is:
'counted' is the definition.
('number' can be a synonym of 'count')
'insensitive? i'm not sure editor' is the wordplay.
'insensitive?' becomes 'numb' (synonyms).
'i'm not sure' becomes 'er' (expression of hesitation).
'editor' becomes 'ed' (abbreviation).
(Other definitions for numbered that I've seen before include "came to" , "Designated" , "Assigned a numeral" , "Enumerated" , "was calculating" .)