Hydrometer Confusion

Okay, I checked my hydrometer today in 80* water (it's summer in Texas) and the reading is .996, which the adjustment for 80* should be .002, right? Is my hydrometer shot, or can I just adjust my readings by .004?

On that point, the English ale I'm fermenting read 1.012 with this hydrometer.

So, is the gravity of the beer 1.008, or 1.016? Normally my brain would be able to get this, but a summer cold has turned it into mush! Thanks.

It's not based on tap water, rather distilled or RO water.

Well duh, that explains it then. I just used some purified water, and the reading is 1.000, at about 58*...

So then my english ale reading is spot on, right?

I would assume so...

Weird, I used the hydro with tap water when I first bought it, I could have sworn it sat at 1.000...

Anyway, I'm happy that after only three days, my best bitter has gone from 1.042 to 1.012, seems that no real agitation is needed, I was afraid that wyeast 1968 would need some agitation to finish the ferment.

Anyway, mystery solved, thanks for the help!

Some people's tap water is 'pure enough' to read 1.000.

others...not so much.