You cannot change your product’s placement on the Grid.
The star rating is a single data point included in the G2 Satisfaction Algorithm that governs Grid® placement. The Satisfaction Algorithm incorporates star rating, review count, and reviewers’ answers about seven satisfaction-related subjects, such as Ease of Use. In addition, the Satisfaction Algorithm takes into account when the review was submitted, with more recent reviews carrying more weight than older ones. For more information on the Satisfaction Algorithm, check out our page on scoring methodologies.
However, the best way to change your product's placement on the Grid is to get more reviews. Check out sell.g2.com to learn more about running a free review campaign