I spend most of my time debugging or extending old code, but then again I'm personally responsible for about 600,000 lines of undocumented code without any test

I spend most of my time debugging or extending old code, but then again I'm personally responsible for about 600,000 lines of undocumented code without any tests (but there are a lot of daily reports which act as monitoring checks). I will say that I rarely need to debug my own code, it's usually old code that needs to be updated due to a data change or business logic change