This is a very simple JavaScript that generates a random number from 1 to 100 every 5 seconds.
You open in it your browser and then resize and move the window to where you prefer it.

Copy the below script and paste it in Notepad.
Then save as rng.html (You may choose the file name, but you need the .html extension.)
Then just double click or open the file, it should automatically open in your browser (Edge, Chrome, ...)



It looks like this by default:


With a little programming skills it's very easy to edit this to your likes.


Editing:

var intervalID = window.setInterval(myCallback, 5000);
5000 is the number in milliseconds that it takes to generate the next number
set to 1000 for 1 second, 2000 for 2 seconds, 10000 for 10 seconds, ...

<h1 id="randomNumber" style="font-size: 100px;text-align: center">0</h1>
add some more inline css style to your preferences, you can easily google css code