fyi: This is twd pro play, so I have no crossbow but inlane feed before making the crossbow shot
Premium/LE probably needs you to cash in when shooting the right ramp to load the crossbow.
No, when you made the weapons drop.. the yellow light above the right ramp will be lit... if you have double playfield and an inlane multiplier ready (for example 4x). Then shoot the right ramp, cash in your inlane multiplier and shoot a crossbow shot.
4x and double playfield = 8x so when making a succesfull crossbow shot: 5M can be worth 40M due to the 8xmultiplier.
If you combine this with for example a running barn mode and you shoot the barn shot this way... you have
5M (crossbow) + 4M (barn) + walker kill/multikill/... = 10M x 8 = 80M in one shot
To pull these things off isn't always easy but this is how you try to play the game continuesley. Multiplay on modeshots, higher multikill values, well walker jackpots, etc...
I have shot 100M riot shots this way too (my riot champ is f.e. now 500M+)
ps: to build your inlane multiplier, shoot lit crosshairs, every 2 shot advances the multiplier by one.