RHF wrote:

Carter - 'decimate' means 1 in 10 [.]

Yup, technically you are right, but yours is the third definition of
three listed in the Yahoo dictionary. The first two were what I had in
mind...[emphasis added]:

1. To destroy or kill a *large part of* (a group).

2. Usage Problem
1. To inflict *great* destruction or damage on
2. To *reduce markedly* in amount

3. To select by lot and kill one in every ten of.