The Acer G257HU has a maximum contrast ratio of 100000000:1. That's over twenty times the contrast ratio of the most common dynamic contrast ratio of 5000000:1.
A 100000000:1 dynamic contrast ratio is in fact the best contrast ratio across all LCD screens that have been around for a comparable time to the G257HU.
A Mega Contrast dynamic contrast ratio is the worst contrast ratio across similar types of LCD screen.
Alternative PC displays that have a 100000000:1 dynamic contrast ratio currently available which you might also want to consider include cheaper flatpanel monitors such as the Neovo FM-24 (£192.88), or the Acer G276HLA (£149.99).