Ladder #246 is five finishes in a row: 12, 43, 63, 94 and 101. You get one turn of three darts for each, and every finish has to end on a double or the bull.
12 is a straight double: D6. If the dart lands in the single by mistake you are left on 6, which still has a double finish with the darts you have left. 43 is a two-dart finish: 3 D20.
63 is a two-dart finish: T17 D6. 94 is a two-dart finish: T18 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.