What is the meaning of Stacking?
In case if you have more than 5 Agents in your company, you need to get additional code(s) like 1 or more codes to stack them under one account. If you have 5 or less than 5 agents then a $59 Plan will work for you. Every $59 plan lets you add +5 more agents to your account.
If you have 20 agents in your company - you would need 4x$59 Plan allowing you to add 20 Agents under your account.