If you wanted to fly INBOUND the VOR on a radial you would need to use the actual radial you are flying on and the use inbound. So if you wanted to fly inbound on the 080 radial so your track was actually 240, you would put 080 inbound.
If you wanted to track outbound you would put in the radial then outbound. So if you wanted to fly on the 240 radial outbound (tracking 240) then put 240 outbound.
In your example about ATC have been kind and told you the radial, you have to think about it when they say take up a track of 075 towards the VOR. As then you would have to put in the reciprocal = 255 and put it in the inbound box (1R). This is the same on an approach with regards to extending the centerline. Easiest with an example. At LGW 26L you are on vectors to the south, to extend the centerline you would go DIR TO CF26L, you want to be going inbound to CF26l, on the radial of 079 FROM CF26L, so you put 079 in the inbound box. If you put 079 outbound the fmgs would sequence the flight plan, as your current next waypoint is CF26l but you've told it you want to fly outbound from there which you're already doing, so your PPOS now sequences and your next waypoint would now be the waypoint after CF, which can really mess up your approach.
Hope that makes sense.