You can use spot and process colors on the same page.

In case you use one spot color only, your color separation would use a total of five plates and five inks - four process inks and one spot ink.

In case you use 10 spot colors (not recommended!), your color separation would use a total of fourteen plates and fourteen inks.

Mixing of process and spot colors together to create mixed ink colors is not supported by GN4 Fred4.