Interview question

A monthly cohort table (hypothetical, data through the end of April) shows customers by first-booking month and the share who booked again in month 1, 2 and 3 after joining. January had 1,000 customers with retention 30%, 21%, 17%. February had 1,200 customers with 31%, 22%. March had 900 customers with 28%. An executive says "month-2 retention is 15%, because only 474 of our 3,100 recent customers came back in their second month". Is that right, and what does the table say?