Currently, in ThemeBuilder, the generated stypes for the Kendo/Telerik Grid component are for size "medium" (or "md").

However, in Kendo UI for JQuery and other Kendo/Telerik suites, the Grid size property supports other values like "small" and "large". 

https://docs.telerik.com/kendo-ui/controls/grid/appearance/sizing 

https://docs.telerik.com/kendo-ui/api/javascript/ui/grid/configuration/size

Consider providing ThemeBuilder templates to allow the generation of styles for other Grid sizes