Years ago, I put a piece of brl paper into my Perkins and brailled a full cell in the first cell of every line. Then I numbered them, in ink, from 1 to 25. I cut a strip about 2 inches wide. I keep it on my desk. In a case such as yours, where the computer layout doesn't give the exact measurements, you can just measure the distance on your strip between, say, lines 15 and 19.
You're correct that according to the TG Guidelines, Section 220.127.116.11 "...One inch ...should be left on both sides of a line or on all sides of an object to be measured..." There appears to be enough space before the first answer choice and between each answer choice to accommodate this requirement. Diane