I was reading about abstract trace space of $W^{1,2}(\Omega)$. They have defined it as
$$W^{1/2,2}(\partial \Omega)=W^{1,2}(\Omega)/W_0^{1,2}(\Omega).$$
Similary I thought we can define abstract trace space of $W^{K,p}(\Omega)$ as $$W^{k-1/p,p}(\partial \Omega)=W^{k,p}(\Omega)/W_0^{k,p}(\Omega).$$
Defining abstractly I can understand but the exponent where the author thought I don't have any idea.
Any help or hint will be appreciated.