Building Steps Up to Code? First Time Attempting Steps
Building codes are talking about the height difference between each finished step and landing, once all treads and finished floors are installed.

You are allowed a 3/8-inch difference in rise between the shortest step and tallest step.
Also, max 3/8-inch difference in tread depth or run
Because the stair code folks love to say 3/8-inch, the amount of tread overhang should be 3/4-inch to 5/4-inch with up to a 3/8-inch variation between the least and most overhang

If you build a staircase where one step is 3-inches different height than all the other steps, people will trip on that step sometimes, and your homeowner's insurance will put the blame squarely on you.
I bought a book about staircases called Building Stairs by Andy Engel when I was doing a few projects at a home I owned where several staircases were falling down.  It was worth the money!  Many libraries are full of good home improvement books too; in my area, you can search online before you even go to the physical library to look.