Not only a negative Radial, but did you notice also the DME is INTEGER as well.
ie Only display whole number of nm, not 1/10 th.
Both of these are cause by some really bad JavaScript coding in the Asobo GNS530.
I strongly recommend to install the GNS530 MOD by @ScorpionFilm422 , which will fix this, and about 100 other things wrong wit the original Garmin GNS530 code.
With the MOD, its like you have a Brand NEW Plane !!!