Clamp
The most a bid may move in a single run. Stops one run from restructuring your account.
A ±15% clamp means the maximum move is 15% in either direction, however far off target something is.
Large single moves are how accounts get whipsawed: a bid jumps into a different competitive tier, attracts a different mix of search terms, and the resulting data no longer describes what you were measuring. Moving in steps keeps each change attributable.