How to set the specific value to the concept template class explicit instantiation?

First, the syntax you are using is for a constrained type template parameter, not a non-type template parameter with constrained type. So the compiler is complaining that it expects a type as template argument, not a value.

For a non-type template argument with constrained type it should be std::unsigned_integral auto num instead.

But then 1 and 2 have type int. They are not unsigned and your type constraint correctly rejects them.

1u and 2u would for example be unsigned integers and accepted by the template parameter.

For a non-type template parameter with a placeholder type not only the value provided, but also the type, is significant.

It looks though as if you really want the type to be std::size_t, not any unsigned integral. So maybe just use that as type for the non-type template parameter instead of the constraint.