I don't really have an exact measurement, but I like my standups to require a pretty deliberate hit. The "hair trigger" I use on my slings and pop bumpers would be wayyyyyy too sensitive on pretty much any other target. But at the same time, you don't want to feel like you've been conned out of points because the ball strike wasn't deliberate enough.

If I'm being honest though, I very rarely find myself having to adjust my standup targets unless they've been butchered by someone else.