You cannot use the photo as it is displayed on the rear LCD as a reliable gauge of exposure.
The problem is the variable ambient light used to view the rear LCD and the fact there is only a very crude brightness adjustment for the rear LCD.
To gauge exposure you have to use the histogram.
But, if you shoot Raw files the histogram (and photo) that is displayed on the rear LCD is a JPEG Basic thumbnail embedded in the Raw file for those purposes.
FWIW - Nikon and other camera makers use marketing mumbo jumbo specifications to make rear LCD resolution seem OMG! wonderful.
In fact the rear LCD has very limited usefulness.
Nikon claims 920,000 dot resolution for their best rear LCDs.
They don't mention that means 306.666 red dots, 306,666 blue dots, and 306,999 green dots.
Nikon more accurately states their rear LCD is - VGA: 640 x 480 x 3 colors = 921,600
What you really have is an equivalent 0.307 MP rear LCD display.
Yep. It's not even 1/2 of 1 whole MP of resolution.