Steps on a promotion?

I am currently grid 11 step 4 and have won a compotion for a grid 21 postion. The hourly rate in the offer letter I was sent has me starting the postion at step 1 of grid 21. Is it normal when going into a hirer grid that you restart you steps or should my wage offer be grid 21 step 4 since I am on that step on my current grid?