Wait - I just figured it out. My highest scores were simultaneously ISFJ, INFJ, INFP, and INTP. My lowest scores were simultaneously ESTJ and ESFJ, which would make ISFJ actually the least likely of my four highest scores. Since I scored three INs, three IFs, and two INxPs, the highest liklihood is that the computer is telling me that I'm an INFP.
So why didn't it say INFP? That makes no sense. Like the above guy said, the computer isn't factoring in the low scores. It seems like it just randomly spit out one of the four highest scores, and went with the S score maybe since more people are S?