Could use some help understanding the four-fifths rule. If possible can I get an easier explanation of what a promotion rate and a minimum rate are?

Thanks

A B E F Minimum Rate Adverse Impact Applicant Pool 48 31 12 22 Entry Level Hourly Employee Hires Hire Rate 18 37.5% 11 35.5% 3 25.0% 5 22.7% 4 5 21 57 56 36.8% 28.6% 9 16 2 Group 3 Caucasian 4 African American 5 Hispanic 6 Asian 7 8 Men Women 10 11 12 13 14 Group 15 Caucasian 16 African American Hispanic 18 Asian 19 20 Men 21 Women First-Line Manager Qualified Candidates Actual Managers Promotion Rate Minimum Rate Adverse Impact 27 11 18 6 17 11 4 17 6 17 43 30 10