This seems like a bit of a silly question,

but I made a few spells, but their costs are displaying as "cost/second" instead of a flat cost.

What determines whether or not a spells cost is displayed as a flat amount or as an amount/second in the UI?

I tried comparing both my spell and magic effect records with vanilla ones, but I can't seem to isolate what the cause is.

Is this one of those things where you need to copy a magic effect record that has a flat cost?