Confused about the Asus XG258q specification page

[csplayer]

Hello, i was browsing the product specification information on this particular monitor and i'm confused about what they say about "Response Time : 1ms (Gray to Gray),0.5ms (Gray to Gray, Min)" https://www.asus.com/Monitors/ROG-Strix ... fications/

Perhaps this is a question more suitable for the asus forums but i appreciate if anyone has any idea. What do they mean by this? Is it 0,5 or 1?
I saw someone mention on this forum that there is 2 revisions of the monitor, the older one having 1ms and new one having 0.5.
Is there any truth to that?