As an Elastic Supply token, GRAVITOKEN uses a negative rebasing to reduce the total supply of tokens in order to increase the value of each token over time. This means the amount of tokens in your wallet will decrease over time, but the value of each token will increase.
Imagine you bought 25% of the market cap. Rebasing means your token amount goes down, but the % of the total is the same.
The value of your investment is not measured by the amount of tokens you possess. Please see the FAQ section here to understand how to track the value of your investment.