It’s only possible to pledge to a project once. Accordingly, backers can choose one reward tier per pledge. You can, however, change your pledge amount and reward selection for as long as a project is live.
For example, if you'd like to back 14 sets, you need to pledge the Hex set and change the amount of pledge to $1070
And here is the calculation: 'Kickstarter Hex Set ($450)' + 'Kickstarter Hex Set ($450)' + 'Kickstarter Dual Set ($170).