I'd ask the tester what their impressions are re whether or not your ds was engaged or was he distracted during the testing, what order were the subtests given in, and their thoughts re what might cause the scatter in the scores. As another poster mentioned above, the tester may bring this up anyway. You can also ask the tester to explain how each subtest is administered (oral questions vs reading etc), how the response is given (oral vs written) and is the subtest timed. With some types of 2e, there will be a pattern in the range of scores based on this type of info.
I am also curious re why you sought out this second set of testing? Was there a concern? Has he had any type of struggles at school? If the reason for testing was some type of concern... then the tester will most likely address that issue in your follow-up interview and let you know if any of the score scatter relates to it. If you let us know what the concern was, it's possible that there are 2e parents here on this forum who have similar situations and challenges who might be able to give you help with understanding the scores.
Last thing I'd recommend - do you have the subtest scores from your ds' WPPSI? My guess is that his FSIQ from the WISC-IV is very similar to the range he received on the WPPSI - they seem like different #s but they aren't terribly far apart, and as another person mentioned above, the scores coming in on WISC-IV seem lower in general than previous the previous WISC. If you compare subtest scores, look to see if you see the same pattern in score fluctuation across subtests (the subtests aren't going to be exactly the same, but they will test similar skills). If you see the same pattern, it's most likely telling you something that's "real" about your ds - but whether or not it's anything to be concerned about depends on what's happening in real life - is he doing ok, or is he having trouble at school? Or do you or his teachers feel he seems to be underachieving?
Best wishes,
polarbear
