Step 1: Divide the number into separate digits:
2994 => 2 9 9 4
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
2 to 9 = 7
9 to 9 = 0
9 to 4 = 5
4 to 2 = 2
Step 3: Combine the filters to a string:
7 0 5 2 = 7052