digital tach symbols

I wanted to know what the symbols to the left and right of the oil symbol on my digital tach. One is a circle and the other is a solid circle. I also wanted to know if I could download a PDF with a instruction manual for this tach. It isn't the multifunction one. It has no buttons and no hour meter. thank you for any answers. Aloha from kona!

[99yam40]

See if this gives you the info you are looking for.

'97 Oil Warning Indicator is Active? - iboats Boating Forums

Thanks a lot. It does help. ALoha!