At a high level, you can think of the Perpetual Ratio as an exchange rate between the vault token and the vault receipt token. For example, using the currency pair for the pound and the euro, GBP/EUR. An exchange rate of 100 would mean that 1 pound equals 100 euros. In a similar fashion, if the Perpetual Ratio of a vault was 100, it would mean 1 vault receipt token equals 100 of the underlying vault token.