The Acer S276HL has a maximum contrast ratio of 100000000:1. That's over twenty times the contrast ratio of a 5000000:1 PC screen, which is the most frequently found contrast ratio.
This PC monitor's contrast ratio (100000000:1) is actually the best contrast ratio amongst all PC monitors of a similar age and spec to the S276HL.
Amongst comparable types of PC monitor the worst contrast ratio is Mega Contrast.
Other PC monitors that have a 100000000:1 dynamic contrast ratio currently available that you might want to consider include the FM-24, or the FM-27 both from Neovo or the Acer G276HLA which has a better Rating.