Sum only first entry

Sorry for all my posts, i promise this is the last :) Just wanted to show, what it ended up being. The solution provided by v-ljerr-msft kept on making issues for me, so i reverted back to the firstnonblank solution. And this was the final, which does excactly what i want everywhere. 

OTP = CALCULATE(SUMX(DISTINCT(DelOrder[OrderLineID]);FIRSTNONBLANK(DelOrder[On Time];0))/DISTINCTCOUNT(DelOrder[OrderLineID]);DISTINCT(DelOrder[OrderLineID]);ALL(DelOrder[Orderline arrival date]))

Never the less, thanks for the help. v-ljerr-msft now i know how to use VAR, and i kickstarted som though processes, that eventually lead to my final solution.