This probability assumption is simplistic, but the point is that it's simple. Given this assumption, it's fairly easy to come up with the odds that any given seed will win any given round. The following table shows the likelihood that the national champion will be a #1 seed, #2 seed, and so on:
| Seed | Championship chances | Odds |
|---|---|---|
| 1 | 0.74326 | 1 in 1.3 |
| 2 | 0.16672 | 1 in 6.0 |
| 3 | 0.05249 | 1 in 19.1 |
| 4 | 0.01947 | 1 in 51.4 |
| 5 | 0.00855 | 1 in 116.9 |
| 6 | 0.00430 | 1 in 232.7 |
| 7 | 0.00220 | 1 in 453.6 |
| 8 | 0.00113 | 1 in 888.8 |
| 9 | 0.00066 | 1 in 1518.3 |
| 10 | 0.00044 | 1 in 2268.1 |
| 11 | 0.00029 | 1 in 3487.4 |
| 12 | 0.00018 | 1 in 5532.6 |
| 13 | 0.00012 | 1 in 8256.3 |
| 14 | 0.00009 | 1 in 11623.4 |
| 15 | 0.00006 | 1 in 17079.8 |
| 16 | 0.00004 | 1 in 26398.0 |
It is important to note that these are NOT the probabilities that particular teams will win. Rather, the probability shown for #1 seeds is the probability that one of the four of them will end up as national champion. (And similarly for the other seeds.) Since there are four teams with each seed in the tournament (and since each follows a theoretically similar path to the title), the likelihood for a specific team to win it all is really 1/4 of the value shown in the table.
The upshot of all this commentary is to guess how many trials the script will run if you tell it to force a particular team as the winner. For example, suppose your team is seeded 3rd. Since each 3rd seed has a 1 in 19.1 chance of winning it all, it will take the script, on average, about 4x19 = 76 trials to come up with your team as the winner. In practice, randomness being what it is, it could take anywhere from 1 trial up to a skillion or more.