6Y5-8350T-82-BK Temp Indicator

[P0BY]

Hey guys! I just installed this new Tach I bought on eBay but it didn’t come with a manual. I noticed a bold line under the Temp indicator that stays always ON. Is this normal? The old Tach was broken when I bought the boat so I have no point of reference.
My motor is a Yamaha150HP 2001 TXRA
Thanks