I used to deal blackjack in the local casinos. bumuming Gamblebot’s playing by the same rules, aces are automatically counted as 11. If that would cause a bust, they’re dropped down to 1, one at a time, until a number below 21 is reached.

So this is how the hand was evaulated:

4 + A(11) = 15. Must hit.

4 + A(11) + A(1) = 16. Must hit.

4 + A(1) + A(1) + 9 = 15. Must hit.

4 + A(1) + A(1) + 9 + 5 = 20. Must stand.

Some more examples:

A+A = 12 (must hit)

A+A+10 = 12 (must hit)

A+5 = 16 (must hit)

A+6 = 17 (probably must stand, if like most casinos)