My googling hasn't been helping me. DD5 has two SAI scores on the OLSAT: 140 SAI as well as an adjusted SAI of 146. Both are 99th percentile for her age, so it doesn't really matter, but of course I'm curious as to what the difference is.

Her raw score was 57/60. Her verbal Sai was 143 and nonverbal 129.

It may be that you have both an age percentile and a grade percentile on your report, rather than two age percentiles. Some schools choose to have the SAI calculated for both. (The SAI and the percentile are derived from the same underlying z score, but in this case, both SAIs would round to 99th %ile.) There is generally a small difference in favor of the age percentile if your student is young for grade, and in favor of the grade percentile if your student is old for grade (e.g., just missed the birthdate cutoff).