The #4d# subshell can hold a maximum of #5# orbitals or #10# electrons. Any given #4d# orbital can hold a maximum of #2# electrons though.
Explanation:
Since #1# orbital can hold a maximum of #2# electrons, and there are #5# orbitals in the #4d# subshell, it can be concluded that there are a maximum of #10# electrons allowed. Coming back to your question, any given #4d# orbital can hold a maximum of #2# electrons.