Your screen determines where these UVB's go -- as posted earlier the T8's need to go inside the tank or no screen -- directly above the basking decor 6-8 inches - the Zilla fixture will take a Reptisun 10.0 T 8 bulb please get one of those --- I think its a 18 inch bulb - the pet stores usually carry them - I would advise you upgrade eventually to a 24" Zoo Med w/ a Reptisun 10.0 T 5 this will come w/ a 5.0 bulb similar to the T 8-- or Arcadia Pro T 5 w/ a 12% bulb - or a Sunblaster Nano Tech 24" you would need to change this bulb out to the Reptisun 10.0 or the Arcadia 12% bulb --- if you need more help please postT5 are stronger bulbs and they last longer. T8's need to replaced at 6 months t5's at 1 year. All in all t5 are better.
A 22 inch fixture it likely an 18 inch bulb. Most recommend a 24 inch fixture with a 22 inch bulb. But as long as your beardie has good access to it either will work.