You mean, that one? https://en.wikipedia.org/wiki/Decimation_(Roman_army) https://en.wikipedia.org/wiki/Decimation_(Roman_army) Then it would be 90 ms -> 81 ms

You mean, that one? https://en.wikipedia.org/wiki/Decimation_(Roman_army) https://en.wikipedia.org/wiki/Decimation_(Roman_army) Then it would be 90 ms -> 81 ms, not 90 ms -> 9 ms. The way I see it, at least. With proper decimation, 90% of what was there remains. ("removal of a tenth", as wikipedia puts it).