The "6c" is not the input of a test case you fail. The error means that you pass "6c" to parseInt (or similar), but it can be a part of a larger input string.
Inputs of test cases should be visible in test case titles, can you see them there?

I think the correct answer should be "4|1". my method returns "4|1" without giving any error.
Perhaps you are counting digits from "4" so you will have "2 digits(4 & |), but in this case the number of digits should be "0 digits".
I hope it helps.