Checkout ladder #238 climbs from 18 to 105 in five steps — 18, 46, 77, 98 and 105 — with three darts per finish and a double to end on.
18 is a straight double: D9. A miss into the single leaves an odd number, so the next dart has to set up a double before you can finish. 46 is a two-dart finish: 6 D20.
77 is a two-dart finish: T19 D10. 98 is a two-dart finish: T20 D19. 105 needs all three darts: T17 14 D20. If the first dart misses its treble, the board will show the new route straight away.
At best the five finishes need 10 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.