Welcome!

Depending on the group - the idea of a reasonable deficit is foreign concept because vast majority have no idea what they burn on average to even deficit from.
Reasonable then depends on how fast they want to lose it, not how much there is to lose.

So the standard method is start at the bottom and build up. Which is great for a house, but most people use too low a foundation and short walls.

How's that for a wacky picture and illustration of a diet!

And welcome in to a reasonable diet that will enhance your exercise improvements to your body.