New LTV is a simulated loan-to-value ratio. It is intended to show you what your loan-to-value ratio would be if the current asset you've selected and quantity you've input were submitted as a transaction to the network and confirmed in a block.
What is a collateral asset?
A collateral asset is any asset that is being used as collateral for a loan. This means that it can be liquidated if your Health Factor drops below 100%. By default, all deposited assets are used as collateral.