I didn't have those results, but basically the FIT test only tests for blood in your stool. It doesn't give any indication of what is causing it. 

Cancer is one possibility but there are many others - a polyp or polyps, diverticulitis, ulcerative colitis, Crohn's disease, an infection, a fissure, hemorrhoids... From what I've read about 1 in 10 of those with a FIT result that indicates there is blood in the stool is cancer. It MIGHT be a little higher with a result of 400, but that means like a 15% chance of cancer instead of a 10% chance. The odds are still against cancer.