Noob ICM question

[playtitleist]

Researching ICM. Working through dethgrind's post. Can somebody explain how the % of prize pool is calculated in his example?

I've played with it, but am missing something elementary I'm sure.

Thanks.

1) you fold
UTG 800
Button 1500
SB 1900
you 3800
36.3% of the prize pool

2a) you call and lose
UTG 800
Button 2500
SB 1900
you 2800
31.5% of the prize pool

2b) you call and win
UTG 800
Button 0
SB 1900
you 5300
42.7% of the prize pool

2c) you call and split
UTG 800
Button 1350
SB 1900
you 3950
37.0% of the prize pool