A dot at the end means that it is only that digit which is recurring, in this case it's 0.6777777777777 infinite times. Two dots on the number on the other hand, means both those digits will form a recurring pattern like 0.67676767 infinite times.

Extending this further, in 0.135, if 1 and 5 have a dot on top, it implies 0.135135135...

Hope this helps