You're seeing just the function uint, go back to Ergo.Numeric module for more information.
Link to this function

uint(opts \\ [])

The unit parser matches a series of at least one digit and returns the integer value of the digits.


iex> alias Ergo.Context
iex> import Ergo.Numeric
iex> context = Ergo.parse(uint(), "2345")
iex> assert %Context{status: :ok, ast: 2345, index: 4, col: 5} = context