It's almost certainly magnetic. Page 12 of the Chart Supplement (sample airport information) has this information at the bottom (emphasis mine):
All bearings and radials are magnetic unless otherwise specified. All
mileages are nautical unless otherwise noted.
All times are
Coordinated Universal Time (UTC) except as noted. All elevations are
in feet above/...
Radials radiate outwards from a station, just like the magnetic bearings on a compass rose. So, the outward radial is just the reciprocal of the inbound bearing.
The key is the “TO” flag. If you were to be flying a heading of 210 degrees you would fly TO the navaid.
Draw it out on a piece of paper, or refer to a chart or your study material. Orientation ...
A radial is always pointing (radiating) away from the VOR. But your instrument shows the TO/FROM indicator as TO. So you are crossing a 210 course towards the VOR, which means you are on the 030 radial from the VOR.
What does it mean to be crossing a radial?
This just refers to the fact that you cannot determine your heading (or track) from the CDI. Based ...