Need Help understanding practice problems.

I am working on practice problems and trying to understand how this works. And one of the first problems I pasted my code in over the “provide one” to see if it would be considered correct. Can anyone help me understand why my input and out put matches the example but when I submit it it tells me it is wrong? Please and Thank you!

Problem = FLOW006

code =

numbers = input("")
n = 0
for num in numbers:
x = int(num)
n += x

input = 12345
output = 15