If your premium exceeds your Thatch health budget, the remainder comes out of your paycheck. The tax treatment depends on where you enrolled:
Plans enrolled through Thatch: The extra premium is deducted pre-tax from your paycheck
Plans enrolled through NY State of Health marketplace: The extra premium is deducted post-tax from your paycheck
This affects your take-home pay and taxable income, so consider the tax implications when choosing where to enroll.