'-p speech/rate=171' option to swiftt doesn't work correctly

[manojb]

If I pass option '-p speech/rate=171' to swift, it makes spoken text extremely fast. Since 170wpm is the default speed I wasn't really expecting the speed at which the text is sploken for '-p speech/rate=171'.
This issue can be reproduced with any text.

Is this a known issue and would it be fixed in the next release?