Grows with time and confidence. My primary hen house and run are on the back of my barn,, in a cleared 1.75 acre area, inside an electric fence that includes about 4.5 acres (its irregular - I took a chainsaw into the woods, and started cutting a perimeter, then strung wire!) Initially, the hens kept the run in sight, rarely ventured into the shaded, underbrushed area at the back of the clearing, and almost never into the woods - stayed w/i about 75' of the run (mostly on the gate side) and largely stuck to the clearings - meaning they skipped under the electric fence that separates my RV from the pasture with frequency.
Now they roam most of the "woods" to the limits of the electric fence in at least two directions, freely roam most of the acre I cleared in front of the pasture, and will freely go where ever I happen to be. Call it 300-400ft in any direction. They only direction they don't challenge is the back electric fence, where underbrushed area transitions into unthinned woods - though I've another several hundred feet of property in that direction, and plan to thin it eventually.