First, we add the two types of days together to find 10+10=<<10+10=20>>20 days in total between the two types.
We then divide this number in half to find Mark's remaining number of days, getting 20/2= <<10=10>>10 days remaining.
Since each day counts as 8 hours, we multiply 10*8= <<10*8=80>>80 hours' worth of days remaining for Mark.
#### 80