The 21.5 is your handicap index on the WHS.
That is then multiplied or somesuch by the slope-rating which is different on every course and on yours it equates to 18.
21.5 on my course off the white tees comes out at 25. So it basically depends on the slope-rating/difficulty of the course.
Yes Ralph my handicap is on WHS. I get that the hole19 app automatically calculates the slope against my handicap. But as I acquired my handicap at the course it seems like I'm being penalised as I didn't actually achieve a handicap of 18 when providing my 3 cards.
Over Winter the greenstaff have installed new bunkers, increased the height of some existing bunkers, added a pond, put in a few new tees and are going to narrow some fairways. All of this is being done to adjust the slope rating.