Let’s look for the numbers in Mayan language(s)
The author of the book “2000 Years of Mayan Literature” (1) has chosen to translate bar-and-dot numerals with their Arabic equivalents. The numerals constructed with bars and dots range from 1 to 19:
Bars-and-dots are used in combination with signs for zero
When numbers modify nouns, they are usually prefixed in a vertical position, but they can also be written horizontally in which case the dots go above the bars.
The number 13
The number thirteen has a significant importance in Mayan calendar and in a measure of time. For example, if measuring from the first appearance of a crescent to a full moon – it will consist thirteen days.
If calculating all major points in a human body (knees, hips, wrists, elbows, shoulders and neck) – that is thirteen too.
While the number of fingers and toes is twenty, and 20 x 13 = 260. By Mayan calculation, the number of 260 days is considered as an ideal interval between the diagnosis of a pregnancy and the birth of a child.
2000 Years of Mayan Literature By Dennis Tedlock, University of California Press, Jan 19, 2010, available online:https://books.google.pl/books?id=_6swDwAAQBAJ&pg=PA155&lpg=PA155&dq=two+seated+men,+marked+as+literate+by+the+pens+in+their+headbands&source=bl&ots=iXoryLyj4L&sig=ACfU3U174ZJJVmD1lHDyXwLwTjM3W7CLkQ&hl=en&sa=X&ved=2ahUKEwishOXjltLrAhXD_KQKHfKwBBAQ6AEwAHoECAEQAQ#v=onepage&q=two%20seated%20men%2C%20marked%20as%20literate%20by%20the%20pens%20in%20their%20headbands&f=false