It depends on the manufacturer and how they spec their cams... Every manufacturer has "their" way of doing it... Some do it at just after .000", some at .001", and some at .006"...
That's why sometimes it's better to compare the @.050" numbers as to the advertised duration numbers, it eliminates the 'room for interpretation' out of the different ways the different manufacturers spec their cams...
One of the reasons that I made my spreadsheets so I could get a better feel for the numbers and try to compare them more accurately...