I don't see three arrows down as any typical proofreading mark. Is it possible that what you are seeing as three down arrows is an indication to insert quotation marks? That's the closest idea that I can come up with. You may need to consult with your proofreader to clarify the symbol. (If someone's willing to read and make marks on your work, s/he will be happy to clarify those marks' meanings.)
In literature, three arrows pointing down can symbolize surrender, a downfall, or a decrease in status or fortune. It can also represent a loss of power or control. The interpretation may vary depending on the context in which the symbol appears.
It means traffic can pass on either side of an obstruction such as an island.
It can go in either direction i think Thomassen
The down arrows are there to scroll down to continue typing up the message.
A downward pointing triangle is often used to represent "female".
I think the "Fallout Shelter" sign
the arrows mean "is eaten by" so for example, if there is a picture of a rabbit with a arrow pointing to a fox it would mean that the rabbit "is eaten by" the fox
Tire Pressure
the arrows in a food chain mean "is eaten by" for example: grass----->rabbit----->fox the grass is eaten by or consumed by the rabbit. the rabbit is then consumed or eaten by the fox hope this helps
low coolant level
Go down the hill.
the horse is your tires . " low air pressure"
it means look down... like they're supposed to be arrows..