Why does it work like this? I was RNG abusing the breeding mechanics in White and it was my second time after being successful on my first attempt, I decided to use the quicker method of listening to pitches. My target was 70 and I attempted to hit it 3 times and each time it hit 71... This drove me to frustration. I did it a fourth time, finding out my starting frame was 49 and I stopped at 69 this time, and it hit 70. I timed all of my button presses, is this normally how it's done or does the frame just advance by 1...?
Are you using a ditto? If so, your frame will advance by 2 when you talk to the daycare man. Even so, I can see that isn't your problem. I suggest starting the game, waiting a few seconds, and then saving, just to alter the WNPC positions. Then try to RNG again.
@Ledujas
Just look at the other frames surrounding your shiny frame. One of those should match the PID of this Frillish. It shouldn't be more than 5 or so frames away.
Chatot pitches...
When you view the summary of any Chatot in your party, even if you only view it for a split second and do not hear its recorded cry, your PID frame advances by one. However, if you do listen to the pitch of that cry, you can match it with the pitches (Lo, Mid-Lo, Mid, Mid-Hi, and Hi) that RNG Reporter (or PPRNG) is giving you. If you start up your game on your seed, enter your menu and scroll back and forth between two Chatots (I suggest you get two, if you only have one, because it makes high frames much easier to hit), you can listen to the pattern of their pitches and match it to a pattern displayed in RNG Reporter. This will help you find your adjusted frame.
If you were in an area with no WNPCs, say in front of Zekrom at the top of Dragonspiral Tower, then you would want to stop advancing your PID frame on the frame BEFORE your target frame. This is because when you hear a chatter, you have already reached the frame, and any further action will increase it.
It's a bit harder for you since there are WNPCs. But it shouldn't take long. You need to figure out how many frames you are advancing in between when you use sweet scent (is that what you're doing?) and when you encounter your Pokémon. Then just adjust accordingly.