That doesn’t look like a leak to me. The library has overhead which will be incurred the first time you use it. In addition, cublasCreate will have some temporary storage associated with it, which will be released when you do cublasDestroy. But that doesn’t mean you get the library overhead back.
You’re just witnessing two different kinds of overhead associated with using cublas library.
A leak would be successive reduction in free memory as you do a create/destroy cycle over and over again.
Also, I would always recommend indicating the CUDA version you are using as well as the platform you are running on.