You're going to love this. ... We are not totally certain! However ...
The majority of the members of NBA's committee on UEB for Technical Materials would place the numeric passage indicator and numeric terminator around a spatial arrangement in cell 1.
But I cannot point to a particular rule or guideline to support that.
Our reasoning could be explained as follows. When you start getting into displayed material, the indentions for runovers can get up to cell 9 and further. In the interest of simplifying and staying consistent, we recommend consistently putting the indicators for a numeric passage in cell 1. [Though we are very tempted to follow Braille Formats and place the indicators for a numeric passage based on those principles.]
Last, but not least, remember the final paragraph of GTM 4.1, which says,
The line above and below spatial calculations should either be blank, or should only contain the numeric passage indicator or terminator.
Braille on!
–Kyle