The ladders technically start from level 0. Google actually had L0s whose job, as best as I could gather, was to take things from point A to point B during, say

The ladders technically start from level 0. Google actually had L0s whose job, as best as I could gather, was to take things from point A to point B during, say, an equipment install. The SWE ladder however starts at L3. With extremely few or zero exceptions, no SWE is hired at L0-2. The idea is that people at the same level in different levels are at roughly the same level of responsibility.