You will need 6 x 1.5/8 buttons (1.5 cm).

Finished measurements;
Bust circumference: 32.5(36.25, 40.25, 44.75, 49, 52.5, 57, 60.5, 64.75)“ 82.5(92, 102.5, 113.5, 124.5, 133.5, 144.5, 153.5, 164.5) cm
Finished length:21.25(21.75, 22.25, 22.75, 23.5, 24, 24.5, 24.75, 25.25)” 54( 55, 56.5, 58, 59.5, 61, 62, 63, 640) cm
Sleeve to underarm: All sizes 15” (38 cm)

Yarn used:
Rowan Summerlite DK
A. 458 Steel - 7(8, 8, 9, 10, 11, 11, 12, 13) balls
B. 468 Silvery Blue - 4(5, 5, 6, 6, 6, 7, 7, 8) balls