Dual Blade's "Attack Speed"

if you can, please survey "Phantom Blow in AS2."
The most easiest way to do it is using stopwatch.

Set timer to 30s, then press and hold "Phantom Blow" key till time up.
You would count the number of times that skill did.


For example, Say that the result was 47.5~.. times.
30000ms / 47.5time =631.578.. =630ms

Its easy.


At least, tell me that
"doesn't happen (or You have mistake)" or "it happens, but we don't know why."