Is this what you purchased? https://reptizoo.store/products/rep...MIvq7m8u7ugwMVTRCtBh2d9wCrEAQYAiABEgKqOfD_BwEi have a 22 inch fixture and i wasn’t able to find a 20 inch t.5 bulb, do you have a link to any? i could only find the 22 inch one, and regarding the sleeping thank you very much that was something i’ve been stressed about lol!
If so I believe the 22 inch bulb would work for it. Looks like they run their fixture sizing a bit smaller than others. Or you can just buy a proT5 by arcadia and return the fixture/bulb you got depending on where you purchased it from. At least with the ProT5 this is tried and true within the hobby. This and choose the 6% bulb option. https://www.reptilebasics.com/t5-light-fixtures-kits/arcadia-prot5-uvb-kit-24-with-bulb/