Hi, good picture of your egg, but i cant see the AC. the AC tell alot. so this egg has been in the bator since May 29th? and you took this pic on the 15th? it looks like it is on day 20, or there abouts, to me. but the AC size tell alot.
When you say the egg is growing more on one side, i am not sure what you mean by that? the shape of the duckling as it grows is larger on one side, in a way, but if you are only turning 2-4 times a day, it should be at lest 4 times cuz the duckling can get stuck or stick to one side of the egg and that is not good when hatching time comes. if you ask @Lacrystol or go to this thread, you can ask Q's there...
https://www.backyardchickens.com/t/...n-chat-meet-new-friends-w-host-sally-sunshine
Incubation for runner duck eggs and many other duck eggs (not all of them) is 28 days. i have had my runner & other duck eggs take 30-31 days but not very often.
Try not to touch the eggs very much except to turn them. and always wash your hands prior to handling your eggs. what is the temp in your bator? are you keeping the room the bator is in at 70 degrees? are you keeping the bator away from direct sunlight? do you have all the vent holes open in the bator? what is the humidity in the bator now?
If they are growing/developing and doing well, i would keep doing what you have been doing & on day 25 i would candle them & mark AC's and if you think they are truly on day 25, i would put them in lockdown and up the temp to 101-102 and turn the fan off, if there is one in the bator and you can put a small bowl w/a damp papertowel in it for humidity, keep it at/about 60%. then listen for internal pipping and when you see external pipping (shell cracking open) i would up the humidity to 75%, keep this as constant as possible, dont let the humidity get below 65% at this point.
I am not an expert and i do not have a high % rate of duck hatchings, so take my advise/suggestions lightly. try the sites above and find other duck hatching lovers here on BYC, get all the advice/suggestions you can.
hope i have helped and not confused you any more?
take care and hope to see hatching pictures soon.