For example, the nonform payrolls number. At the time it is initially announced, it was based upon so-called Established survey, interviewing about 119,000 business and government agency. This is a sampling process. And it will be adjusted by seasonality and the closing and opening of business. In short it is an estimate.
Then BLS will compare the estimate vs. the actually tax number in the later date when it become available. The difference is reported as revision.
During Trump presidency, there were a lot of revision as well.
It is part of the process.
