We have specific guidelines / process that we use to measure each. For example, professional coding is a focus on writing clean code, that is well designed on the micro level (good names, good modularity on the function / class level), and good testing. We measure this using a rubric as we watch each engineer code. Low-level understanding is knowledge of how computers work, under the hood (bits, bytes, character encoding, operating systems, networking, etc). Again, we have a rubric (and these topics are covered at multiple points as each engineer goes through the process). Our measurements are not perfect, but companies really do vary widely in how much they care about different areas (understanding how computers work say, vs. having a great coding process). By mapping this and matching we save everyone pain. No one had tried to do this before, and I am pretty excited about it.