What does the seven-day transcoding of Changsha yellow code mean?

/kloc-within 0/4 days, give a yellow code to those who have the following conditions: the space-time companion of the confirmed case or asymptomatic infected person who may be exposed. People who have lived in cities and counties where high-risk areas are located or potential communities to spread risks. Have a history of living in the city and state where the moderately dangerous area is located. People entering Hunan from local epidemic provinces.

Those who are given the yellow code will receive SMS reminders. Please follow the SMS reminder to implement the prevention and control measures, and carry out COVID-19 nucleic acid testing as required: conduct 7-day testing for the time and space companions of people who may be contacted by confirmed cases or asymptomatic infected people, and residents living in counties and cities with high-risk areas or potential community transmission risks. For those who have a history of residence in the city and state where the medium-risk area is located, check it twice in 3 days. Conduct 1 test on people entering Hunan in provinces with local epidemic.