bump-steer ?

[cjperformance]

There is no magic figure for toe in. It is determined by many things, basically you actually want the tyres to run parallel, (not toed in or out), when the vehicle is in its most used/average speed range and running in a straight line.
This is worked out/affected by things like, castor angle= ammount of pressure on tyres trying to give toe in or out,
bush material= the softer the bush material or the more bushes in the set up the more toe in you need to combat frictional force which wants to create toe out,
tyre width=rolling friction which depending on rim offset and suspension design can increse dynamic toe in or out.

The same car with the same suspension will require a different toe setting if you change, rim offset, or, tyre compound/type, or, bush type-rubber/urethane/solid, or, almost any other thing.

on the track you will want a different toe setting for a track with lots of corners and minimal or sloe straights as compared to a fast track with long higher speed straights and lighter corners.
For some drag apps with a basic front end that runs solid bushings, 0 camber and a some castor for stability and thin tyres you may need very minimal toe in.

On some AWD/FWD apps you may actually need some toe out to allow for the driving force thru the front wheels being able to pull some toe in, this depends on the suspension goemetry of course.