It's whatever split maximizes the value of the 5th runner, provided that the 5th isn't greater than any of the proceeding (and to the extent it's possible). In your example 10 > 2, hence selected.

a simple change fixed it, but annoying nonetheless. this wasn't anything complex or reliant on an external package; it's a legit error with this site's interpreter

your problem is trying to write code that works in R lmao

Wrote some code in R. In RStudio the code worked flawlessly on the sample tests, yet in the test it produces dramatically different results. For example, when I run the first test case in RStudio, the first chunk correctly outputs "ijJ tipvme ibw", however here as part of the test (same code), the result is returning "ij10 209162213"