Faint second line after the time frame

This morning I took a first signal pregnancy test (Walmart brand), looked at the test a couple mins later and didn't notice anything. A few minutes after that I took off and went to work. Well I recently came home and noticed a very faint second line. I know you're supposed to disregard after the 10 min time frame, but what is the chance it's actually positive? I tested the past 2 days with the same test, and those ones don't have any line with color, just indents.