There are two types of ranking methodologies. One for individual leagues and a different one for overall rankings.

Individual league ranking

Overall ranking (All, Huntsville and Madison)

You are presently ranked 325
Your previous best win is a player ranked 150

Scenario 1
You defeat the player at ranking 180
You will immediately be ranked 180 and player 180 moves to 181

Scenario 2
You defeat the player at ranking 120
You immediately move to 150 (your previous best win) and a new best win of 120 is stored

Note: If you do not defeat anyone better than you (ie your previous best win of 325) within a specified amount of time (normally 13 months) then this best win will be eliminated (considered a fluke) and your best win will be reset to the rank that you are presently at, in this case 325.

As can be seen, a player can move many ranking positions instantly but there is a check to stop movement if the player's previous best win is determined to be well above their consistent skill level.