How big is the risk of pregnancy if the condom breaks?

Hello, yesterday during our approach my condom broke (during deeper insertion, it broke at the very end) there was no ejaculation, we immediately realized and stopped intercourse. Theoretically, the girl had 3 days of ovulation at that time, although I know that there is nothing to suggest it, the more that the previous period was 10 days late (probably because of stress because a month ago she also burst), but fertilization did not take place. How big is the risk of pregnancy in this case? 20 years