the default – as coming from SGP – is zero. The actual minimum setting is very much mount dependent. As Chris already explained, some drivers enthusiastically report “slew completed” while the mount is still adjusting the final position. Another issue is that, after an eastward slew, there is a dead time when the scope is not tracking while the mount gear “consumes” the RA-backlash.
So, for a very high-quality mount, a couple of seconds should be OK. For a normal mount, 10 to 20 sec might be necessary. To be honest, I never tried to optimize that setting, given that it is only active during the target acquisition and after a meridian flip.