It would be a better to set this in Mach3
menu config/port&pin, spindle setup tabs
in the general parameters 'box', CW Delay Spin Up > give a value in seconds or ms depending of the setting in the general config (right most column > G04 Dwell in ms)
if Dwell is in ms, enter 3000 in 'CW Delay Spin Up', otherwise, enter 3
PS: I f you are using an Ethernet smoothstepper, the delay is always given in seconds, even if mach is set in ms.