  We obtain truncated restriction estimates of an unexpected form for discrete
surfaces \begin{align} S = \{\, ( n_1 , \dots , n_d , R( n_1 , \dots, n_d ) )
\,,\, n_i \in [-N,N] \cap \mathbb{Z} \,\}, \end{align} where $R$ is an
indefinite quadratic form with integer matrix.
