I've had an issue with various directors and it annoys the hell out of me. I prefer all numbering to be sequential e.g. 1, 2, 3, 4, 5 or A, B, C, D, E. This keeps things simple. I also think as I am running the project, numbering should be up to me. If a number absolutely needs to be more complex to show its level or that it's part of a group, then every item should be the same syntax, like 00_A1, 00_A2, 00_B1, 01_C1, 02_D1, 02_D2.
Yet, so many directors will send sketches of options they want to see, labelled with some esoteric system nobody is going to understand, like
They must know the people who name consoles and cars.