The A and B columns refer to two different agitation methods, each with its own matching development time. In practice, you pick one method and use the corresponding time.

From the community answers, the chart appears to mean:

• A: frequent agitation — e.g. agitate every 3 seconds / very often during development
• B: standard intermittent agitation — e.g. about 5 inversions of ~3 seconds each at the top of each minute

For example, for FP4+ at 1+10, one reading of the chart is:

• A: develop about 5 minutes with very frequent agitation
• B: develop about 8 minutes with 5 inversions each minute

A good general practice, even if not clearly stated on the bottle, is to agitate continuously for the first 15–30 seconds after pouring in the developer so the film is covered evenly, then switch to the chosen rhythm.

If some values are in bold, those are usually the preferred combinations. If a cell has a dash, that combination is not recommended.

If you're unsure, the safer, more conventional choice is usually the B method: initial continuous agitation, then a set of inversions once per minute for the listed total time.