Of course, we all know that Reagan went from there to win re-election in a landslide.
So for Trump to be at 46% at this point (essentially tied with where Reagan was at this point) is pretty astonishing considering the constant beating that Trump has been getting in the mainstream media.
The higher approval does a couple things as well.
It undermines efforts by Republicans to primary Trump and efforts by Democrats (and some Republicans) to impeach.
I expect it to jump higher after Feb 1, when Americans see their paychecks increase.