What is the appropriate number of invitations from the recruiter?

Recruiters invite 15~20 people every day. One of the easier people is to be a recruiter. Their salary is generally a basic salary plus commission. Although their jobs are easy and their wages are stable, they also have a certain amount of tasks, and the average daily recruitment invitation is between 15 and 20 people. And they have to interview people when they are busy at work, which is about 10. Especially in the recruitment season, candidates may interview for one month in a row.