Stranger Eons features many mysterious symbols. The meaning of most is currently unknown.
It's meaning may be related to the title of the story and it's probably a word in the language of the Guardians.
A set of 9[?] symbols seen in various places, most notably on the on the Chapters page. &'s message has confirmed that this list is ordered:
The symbols are visible on "test tubes" in Vekh's lab and they seem to correspond to development stages of the organisms inside the tubes.
Over certain doors inside The Tower, these symbols are displayed, restricting access to various levels. It's not fully clear what the symbols actually measure.The symbols seem to be the same as the ones on bio-weapon chambers, which suggests similar origin.
When a person approaches the door, it displays its requirement, seen below for Ryann and Sari.
If access is granted, the symbol turns light blue. If access is denied, the symbol and the lines underneath it will flash red
In Sari's case, the access seems to have been overridden and another orange/yellow symbol is displayed on top of the red one. It appears to be a lower requirement. This event was a surprise to Eyeball and Countless Leaves and the origin of the override is yet unknown. 
What is noteworthy: the requirement may vary depending on the direction of one's travel, shown below is the same door approached by Ryann, but on the other side from Sari's perspective
The empty circle probably represents the lowest possible restriction. Based on Sari's interaction with the door, it may be assumed that Sari's level is below the 1=L7 symbol, and possibly atthe circle with a + and three lines above.
Seen on the clock, the asteroid boxes and in various other locations. Used to label Tarot cards. They're also used to represent time until certain events on the computer panel. They represent numbers in bijective base 12[], hence there is no symbol for 0. Numbers are written left to right starting with the most significant digit. Negative numbers are represented with a dot to the left of the number.
Their order on the clock may be wrong, since the clock will be changed in the future.