(I'm one of the Directors of the contest, so I know of what I speak.)
"Score" is a terrible title. It should be "penalty".
The teams are ranked first by the number of problems they got correct. Thus St. P's came in first, because they were the only team to get 7 problems correct. Among the four teams that got 6 problems correct, they are ranked from smallest penalty (KTH) to highest (MIT).
Penalty is computed as the total cumulative time it takes you to solve a problem. So if you solve one problem after 30 minutes and a second problem after 30 additional minutes, your penalty is 90 minutes (30 from the first problem, 60 from the second). In addition, you are given 20 minutes of extra penalty for each incorrect submission to a problem that you eventually get correct.
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(I'm one of the Directors of the contest, so I know of what I speak.) "Score" is a terrible title. It should be "penalty". The teams are ranked first by the number of problems they got correct. Thus St. P's came in first, because they were the only team to get 7 problems correct. Among the four teams that got 6 problems correct, they are ranked from smallest penalty (KTH) to highest (MIT). Penalty is computed as the total cumulative time it takes you to solve a problem. So if you solve one problem after 30 minutes and a second problem after 30 additional minutes, your penalty is 90 minutes (30 from the first problem, 60 from the second). In addition, you are given 20 minutes of extra penalty for each incorrect submission to a problem that you eventually get correct.