Hard to say what your variance will be because after you broach the parallax setting your eye position behind the scope comes into play.
The best way to answer your question is this: Most fixed parallax scopes will have roughly a 1" error for every 100 yards before and past the parallax setting. If you are shooting for accuracy from a bench and measuring your groups, this could get frustrating quickly. But in a hunting situation a 1" variance is hardly a problem (unless we're shooting prairie dogs at extreme distances). To get the most out of your scope, or any fixed parallax scope, it is best to zero at the parallax distance and adjust your POI from there at distances you shoot.
I'm not a "turret cranker" and prefer to use a dope sheet if holdovers are necessary. And in a predator hunting situation I've never had the time to turn a turret anyway. In other words ... use a ballistics calculator (several online) and set the zero distance at 150 yards. Then you will see the adjustments you will need to make at other distances.
Parallax error on fixed parallax scopes will always be there unless the shooter can get behind the scope in EXACTLY the same position EVERY time. And I've never known anyone who could do that ... especially in a hunting situation.
HTH.
