There is none. 25, 35, 50, 75 are all common.
I would say to sight in at distance you will be shooting. If that is variable, or for hunting, try 50-75.
FWIW, when my kids were little and we did target shooting, we sighted at 25 and shot at 25. I wouldn't site at 25 for hunting unless my shots were going to be at 25.