Thank you, Julie—
This question forced me to look at super and subscripts in different sections of UEB Guidelines for Technical Material and had wondered if the second superscript indicator would have the effect of adding another level above, making the  in a super-superscript position. But the grouping indicators seem to alleviate that worry. I think I'll go with the superscript indicator on each number. I would only need the grade 1 on the  since the second indicator —before the  —follows a number and is already in grade 1 mode, correct?
Thank you again for your fast response.