Ditto master of none's advice. I'd also suggest googling something like "WJ-III Tests of Cognitive Ability" + subtest description (or WJ-III Tests of Achievement for the achievment tests) to find a detailed description of each test and go over that before your meeting. Also be sure to ask for details about each at your pre-meeting tomorrow.
Did your report include a list of which subtests go into each cluster group? If not, ask for that info too. For example, on the cognitive tests, which subtests are used to calculate Thinking Ability etc. Each of my kids has had the WJ-III Cog test and if I recall correctly, some of the subtests are used in calculating more than one cluster.
Re why would one memory-related task be a lot higher than another, the subtests are all very *very* specific re what the student is asked to do, so what you need to do is understand exactly what the subtest requires the student to do (what type of prompt is used, what type of response from the student, oral vs written etc, and what skill is the test measuring). Ask the school psych tomorrow at your meeting. I don't have a description of the subtests with me at the moment, so I can't help you with test specifics.
It might also help us here, if you could tell us why you're suspecting 2e - what type of struggles is your ds having at school? What prompted testing specifically?
Also, and this is just a fwiw - I have two 2e kiddos, and they had lower scores on their "low end" when tested with the WJ-III... so this is just a guess, but I wouldn't be all-out surprised if your school psych told you that your ds' scores are all "within normal range". That doesn't mean the discrepancies aren't significant or aren't impacting your ds, it's just that schools are often looking for much lower "low end" scores to meet the cut-off bars for services. If the school staff start saying "it's all average and good", rather than pointing to discrepancies from low-high on testing, we found it was most helpful to bring the conversation back to our children's actual schoolwork samples to illustrate the problems they were having (but that's just our experience in our one school district).
Best wishes,
polarbear