Checkout ladder #223 climbs from 40 to 110 in five steps — 40, 60, 79, 88 and 110 — with three darts per finish and a double to end on.
40 is a straight double: D20. If the dart lands in the single by mistake you are left on 20, which still has a double finish with the darts you have left. 60 is a two-dart finish: 20 D20.
79 is a two-dart finish: T13 D20. 88 is a two-dart finish: T16 D20. 110 is a two-dart finish: T20 Bull.
One route here finishes on the bull (T20 Bull for 110); it counts as a double.
At best the five finishes need 9 darts out of 15. Your result counts the finishes you make first and the darts you used second. These are friendly numbers. Aim at the inside half of the double on the first dart — a miss on that side lands in the single and keeps the finish alive.