Small or large, deep or shallow, these are the things you need to know before starting to do a patch repair on concrete whether it be vertical elements (such as walls) or horizontal elements (such as slabs).
But don't forget, the most important part of any repair, is the "Substrate Prep". The original concrete need to be clean, and all the loose particles, debris and ... must be removed. Even in some cases, the patch area needs to be squared out too.
Sometimes, you may even need a primer for your patch repair product. The primer is usually a low viscosity (runny) epoxy product.
If you see corroded reinforcement bars, you may need to remove and replace them too.