You need to generate a large number by using the special Alex's Number.
The instructions are shown in the interactivity but if you want to get them before then here they are:-
1/ Drag a number from “Drag Numbers” into the “Feedback” to replace the 0.
2/ On the Right Hand Side click “Run”.
3/ Click “Run” two or three more times
4/ Take a look at Alex's new number, you need this for the challenge.
The challenge is to write down the value of each digit from Alex’s big new number.
When you’ve done that click "Reset" and drag in a new different number then repeat instruction 1/ 2/ 3/ 4/ as before.
To start click on the image below.