When you stake your LPs into our auto-compounding farm, you get back shares of the pool, recorded as vLP tokens.
The pool is constantly growing due to compound interest. Your share stays constant, but each share will represent more and more LP tokens as the pool compounds.
On the main webpage, you can check how much LPs you current stake in the pool and their USD value.
When you click the minus/withdraw button, what you're actually doing is burning the vLP tokens in your wallet and getting back the LPs. The website interface manages this for you.