Two is written as two dots. A day numbered two stands in the second place of whichever trecena it belongs to, one day past the sign that names that run, and the count proceeds by advancing the number by one and the sign by one simultaneously, so that the two cycles of thirteen and twenty turn together like meshed gears.
That simultaneous advance is what generates the 260 distinct combinations. Thirteen and twenty share no common factor, so every number meets every sign once before any pairing repeats, and thirteen times twenty is 260. Nothing further needs to be stipulated; the length of the count follows from the two cycle lengths alone.
Maya numerals are written with a dot for one and a bar for five, and the coefficient of a day is written in exactly that way in the inscriptions, set beside the day sign in its cartouche. The system is positional and includes a sign for zero, which is why the Long Count can be written as a string of places, but within the 260-day count no number above thirteen ever occurs and the notation stays simple.
The word Lunar, attached to this coefficient in modern popular literature, comes from Jose Arguelles's Dreamspell of 1987 and not from any Maya source. The thirteen coefficients in the living count kept by highland Guatemalan daykeepers are simply the numbers, and no separate names for them are recorded in the Classic inscriptions or the colonial sources.
Sources Maya Hieroglyphic Writing: An IntroductionJ. Eric S. Thompson with Dreamspell: The Journey of Timeship Earth 2013Jose Arguelles