How do handicaps work in Masters racing?

Rowing Australia publishes Masters handicap tables in Appendix 10 (Masters Handicaps, last updated September 2022 in the tables). Appendix 7 says the handicaps that apply at the Australian Masters Rowing Championships are those in Appendix 10.

• Tables: there are separate tables for men's, women's and mixed events, set out by boat class and age category (A to M, with an N row in the men's single scull table). Each table gives handicap times in seconds against the category, headed "Time (Seconds)".
• Where handicaps are used: events with low entries combined into one race, the Champion of Champions single sculls (run with relevant handicaps as a straight final), the Champion Club Eight (handicapped), Mixed events (run as handicapped divisions rather than heats and finals, with medals for each division), and a C-Grade crew admitted to an Interstate Masters event.
• Coxed versus coxless boats: Appendix 10 recommends additional handicaps when coxed and coxless boats race each other, used in addition to the age-based handicaps and relevant to 1,000 m racing only. For example the men's 4- or 4x- is listed at 7 for categories A to D, 8 for E to H, 9 for I, 10 for J and K, 11 for L and 12 for M.
• Substitutions: if a crew member is substituted in an age handicapped event, the handicap is updated to reflect the revised average crew age (Rule 60.4).
• Intergrade: the appendix also has intergrade handicaps for individual years within the K, L, M and N grades in the men's single scull.