Five numbers, three darts each, doubles only to finish: ladder #233 asks for 20, 49, 72, 100 and 101.
20 is a straight double: D10. If the dart lands in the single by mistake you are left on 10, which still has a double finish with the darts you have left. 49 is a two-dart finish: 9 D20.
72 is a two-dart finish: T20 D6. 100 is a two-dart finish: T20 D20. 101 is a two-dart finish: T17 Bull.
One route here finishes on the bull (T17 Bull for 101); 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.