What is stacked versus non-stacked UM coverage?

Video Transcription:

When purchasing UM coverage under your personal automobile policy, you'll have the option to elect either the stacked or non-stacked version of UM coverage. Under the stacked version, you purchase the policy amount, and based on the number of cars you own, the UM amount itself doubles. Under the non-stacked version, the amount that you purchase remains the same regardless of the number of vehicles that you own..