Countdown numbers in Sonic 1... "bug"?

It seems the countdown numbers are showed in the screen where Sonic is in the moment that the number appears... Everything seems to work fine, but sometimes this not work properly. If Sonic is near the top of the water, the numbers change its position even if I don't move Sonic... I'm not sure if it depends of where the top of the water is or what, but I don't find any clue of why is this happening... any idea?

The routine that change the position of the number is in "Obj0A_ShowNumber", but that routine works fine, so maybe something is changing its position in other place...

Here some shots of the "bug" (in original Sonic 1):

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I didn't move Sonic and, as you can see, the numbers are showed in different possition...

 

That's not a bug, I thought that was meant to be?

 

Really? And what is its purpose? I mean, why this only happens if you are near the top of the watter and not if you are completely underwater? And where is the part of the code that make this to happen?

I noticed this because I was changing the position of the countdown numbers, so I edited the code that is in "Obj0A_ShowNumber", but the position is still changed a bit sometimes when you are near the top of the water level (like I show in the screenshots and like it happens in the original Sonic 1).

 

Well, probably because that if the game loads the countdown numbers outside the water line, it'll repeat the number or it'll show glitched tiles.

This "bug" doesn't happens with Sonic 2 so the results are those real bugs I've mentioned above, you can see that in this picture.

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Yes, but in Sonic 1 the number is showed well, what I want to avoid is that thing that makes the number change its position even if you didn't change Sonic position...