Your calculations are wrong.

Please correct.

First example should give 12x40 since payout is 2:1. With a total of -40.

Third example has 10 on 1st doz and 5 on both 2 and 3? If so, results are wrong.

Yes, correction: 20 on 1st Dozen

W12 L26

Win 12 x40 = 480

Lose 26 x-20 = -520

Total = -40

10 on 1st Dozen, 10 on 2nd Dozen

W24 L14

Win 24 x10 = 240

Lose 14 x-20 = -280

Total = -40

10 on 1st Dozen, 5 on 2nd Dozen, 5 on 3rd Dozen

W36 L2

Win on 1st Dozen = 12 x10 = 120

Win on 2nd Dozen = 12 x-5 = -60

Win on 3rd Dozen = 12 x-5 = -60

Loss on 0 & 00 = 2 x-20 = -40

Total = -20

Betting $20 on the 1st Dozen will lose $40 after 38 Spins. Betting $20 ($10 on 1st Dozen and $10 on 2nd Dozen) will lose $40 after 38 Spins. But Betting $20 ($10 on 1st Dozen and $5 on 2nd Dozen and $5 on 3rd Dozen) will only lose $20 after 38 Spins. Bad Bet. Whoever thought of Betting on all 3 Dozens at once or all 3 Columns at once? Saliu mentions it. But, still, isn't it strange? Some of you aren't very nice. It took a long time for me to be a nice guy.