Reduced tensor product on the Drinfeld center

The annulus comes with a "stacking" operation which glues two annuli into one. This provides tensor product structure on the category of boundary values $Z_{\text{CY}}(\text{Ann})$ associated to in an extended Crane-Yetter TQFT. It is known that $Z_{\text{CY}}(\text{Ann}) \simeq \mathcal{Z}(\mathcal{A})$, Drinfeld center premodular $\mathcal{A}$ from $Z_{\text{CY}}$ constructed. We give explicit formula for $\mathcal{Z}(\mathcal{A})$ corresponds stacking $Z_{\text{CY}}(\text{Ann})$.