EDIT: Uhh, yeah... on a newfound common sense suspicion I decided to check a second later after another couple times where I managed to hit a second early... And of course the second later had the same exact roamer locations on the same delay. Derp moment from me. Think this might be worth noting on the first post. I doubt I'm the only one who's made this mistake... A helluva lot of frustration for something so silly. >_>
Guess I'll be putting 0 in the seconds boxes in the future as you advised.
Same thing was happening to me when I was trying to RNG the Celebi a while back, I figured it out pretty much the same way you did lol. I figure keeping the +/- 1 second is good when you can't confirm your seed via Elm due to low frames on a spread(I had one of 5 a few days ago). Glad you figured it out though.
Using Eon Timer, I timed pressing A on the continue screen to when the second timer hit 0. I got 690 delay instead of the target 630. Yet when I button mash and ignore the second countdown, I get close to 630. Is this supposed to happen...?
Just to clarify you're starting the game when the first time hits zero correct?
Nah, this time my calibrated second was correct. I mean, I guess all I can do is continue updating and hope stuff works out...
It's awkward because before I RNG'd successfully with often the wrong second (for Wondercards).
I'll see if updating and trying to time it properly instead of mashing can actually get me the result tomorrow, fingers are dead right now. I just find it weird because in trying to get a Celebi with the right nature I've gotten perfect IVs nearly 10 times now, but I don't think I'm RNGing correctly. Though now to make it worse when I hit my delay the IVs have been off the past 3 times, and I'm quite sure the frame was advanced properly. I'm just starting to get unsure about the process now. Urgh.
If your confirming with Roamers, as was previously mentioned, you can have the same result for different seconds, EX: Your Target Time of 9:54:34 has the possibility of having the same roamers as 9:54:33. If you have frames to spare Elm is much more reliable.
As to the frames being off it could be several things, a mart with NPC(Cerulean has none), lack of adding 2 to the method 1 frame, accounting for 10 Elm calls even though RNG Reporter now confirms with 9 (I did this for about an hour one time), Roamers not being accounted for etc.
If you get an off the wall IV's plug them into an IV calculator and the plug your seed into the main screen to scan the frames near your desired frame(remember to look for -2 of the Wonder Card frame for method 1).
Hope some of this helps you