You got some good answers a few days ago.
What type of client are you trying to help, or why are you needing these particular standards? Although it’s kind of nice to see how well we stack up to others, the most useful data are often self v. self at regular periodic intervals.
Time? As in how long to hold a plank? I have read a great deal of material that indicates that holding plank for longer than 10 seconds has not been shown to improve strength or control in any other posture or body position. There has been some evidence that doing movements in the plank position translates to great engagement and stability, but more research/data needs to be accumulated before any solid statistics can be of much use in making recommendations beyond a ten second hold.