Hi snomhf,
The ">" is the range-indicator, the number "824" is the closure-rate. The ">" is moving with the PDT on the (vertical) Y-Axis from the VSD. The 5 horizontal lines of the VSD are a kind of range-scale, which depends on the selected range of the radar. On page 86 the radar is set to 40 miles so the distance for every horizontal line is (fromt down to top):
1st line (bottom): 0 NM
2nd: 10 NM
3dr: 20 NM
4th: 30 NM
5th (top): 40 NM
On page 86 the ">" and the target symbol are slightly above the 3rd horizontal line, which means that the range to the PDT is about 24 NM. Hope that helps.
P.S.: Sorry for my bad english, I'm german :)