Passing a same random number to all tests in Cypress

So I have two tests - Test1.spec.js and Test2.spec.js and I want that with every test run a random number should be generated and the same random number should be used in both the specs. I wrote a simple Math.random() function for this under support/index.js

Cypress.config('UniqueNumber', `${Math.floor(Math.random() * 10000000000000)}`)

And in the tests I am writing as:

cy.get('locator').type(Cypress.config('UniqueNumber'))

When I am trying to execute the tests using the cypress app npm cypress open and then Run All Specs, a random number is generated and the same is passed to both of the spec files correctly. But when I try to run the tests using the CLI npx cypress run for both of the spec files different random numbers are passed.

What am I doing wrong in case of executing the tests using CLI?