This is a space of vector valued Siegel modular forms with real representation $\mathrm{Det}^{ 19}\otimes\mathrm{Sym}^{ 8 }$. The following table gives the dimensions of various subspaces of $M_{19, 8}(\mathrm{Sp}(4, \mathbb{Z}))$.

Total7
Non cusp0
Cusp7