Chain sizing for grx 1x 11 spd

[GregR]

Hi, I replaced a chain on a cross bike with 11 spd grx. Normally I would size to the old chain, but it was broken, and repaired on the trail by others with unknown changes. So, I sized it like I would on my road bike. (big big, add 2 links) OK, I'm the last to get the memo to add 4, 5, or 6 links, depending on whether you use a quick link or not.
I used a quick link, so 4 or 6. I read tfm but it doesn't seem to say when to add 4, and when to add 6.
Can anyone give me some guidance on whether it should be 4 or 6 links added?
Thanks in advance!

[robbosmans]

+4 links