Glow vs FF??

So i have been inputting my bbt & opk results into both and i just realized they gave me different O days...i wanna say Glow is right, and if it is then Im guessing I missed the egg...??... So FF said i O'd on CD 16, yet my first Solid Smiley was on CD17, i tested @ 9am-9:30 everyday, til after i was done i was informed the surge can be picked up from 11am onward?? Because it takes time to get in ur urine...Anybody else heard of that?? And well according to Glow i O'd on CD18...??... So on FF im 10dpo & on glow im 8dpo...and well CD18 we didnt BD only the 3 days before and well from the day after aswell...😑😑