Step 1: Divide the number into separate digits:
5780 => 5 7 8 0
Step 2: Calculate the distance between each digit and the next (the last digit with the first):
5 to 7 = 2
7 to 8 = 1
8 to 0 = 8
0 to 5 = 5
Step 3: Combine the filters to a string:
2 1 8 5 = 2185