Why is my health code yellow?

Maybe it's because my phone number and confirmation number are in the same space-time grid (the range is 800 m× 800 m) * * and stay for more than 10 minute.

Time-space companion means that my phone number and confirmation number stay in the same time-space grid (the range is 800 m× 800 m) for more than 14 minutes, and the cumulative stay time of any number in the last 14 days exceeds 30 hours, and the found number is the time-space companion number. My green health code will turn into a yellow code with warning nature, and will be marked as "time companion" by the system. Health code yellow code personnel and space-time risk personnel accompanied by SMS reminders should immediately report to the community, and conduct two nucleic acid tests within 3 days, and the interval between two nucleic acid tests should be more than 24 hours. Please stay at home and don't go out until you get a nucleic acid negative result.