Elevation (ʿulūw) commonly concerns fewer links to a specified point, while descent (nuzūl) involves relatively more intermediaries. Yet the quality of a route depends on its narrators and supporting indications, not number alone.
Absolute elevation means closeness in transmission to the Prophet. Relative elevation compares closeness to a specific imam, compiler or shaykh within a recognized reference chain. A route may be high relative to a compiler without necessarily having the shortest total path back to the Prophet.
Hypothetically, chain A has five links to the Prophet and chain B has seven. A is higher numerically, but if a transmitter in A is weak and B’s narrators are strong and precise, B can be preferable for authenticity.