Flying at night in a SEP is what he is refering to.
I always think of the night xcountry bit of the Night training as the bit where you try and show the student how fecking stupid it is flying anywhere at night with only one engine. Actually I did my night restriction removal in my FIC. I would advise against this now, you really don't need the stress and danger involved in training at night until you have a fair few hours instructing under your belt. It was the blind leading the blind me with 6 hours sep at night teaching them!!!! Now i would say you need at least restriction removed and also 20-30 hours yourself before being allowed to apply for the night restriction to be removed.
And before you start say how likely is that, i have had to take the family of a dead student over the point where he ditched at night with the instructor on night training. Not very pleasant i can tell you.
MJ