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...
this means that you have a low coolant level
Low Coolant Level. There is not enough coolant in the reservoir.
low coolant level
downbeat downcast downgrade downhearted downplay downpour downspout downstairs downtown downwind