Yep, like Rob said, you can have it immediately PWO if that’s how your schedule falls. Guys have done that in similar situations. It’s not “ideal” because you’re not really getting a big protein pulse due to the Plazma still rolling around in your system, but there’s really no wrong time to have some Mag-10.
With that in mind, though, you could try having it with that PWO meal instead of right after training. It’d let the aminos in your system drop a bit (which is a good thing and potentiates that anabolic pulse), and the hydrolyzed casein in Mag-10 basically jump to the front of the digestive line when you eat, so you’re not really slowing it down by having it with food.
Long story short, either way is fine. Try both if you can and see which feels better.