Do you add any spaces on the text line that enclose in the spoiler commands? That can sometimes lengthen the bar. That is if I'm understanding things correctly.
If i understand correctly, you are asking me if i add spaces on the line that the spoiler code exist. I messed with that a bit. I tried to do the spoiler on it's own line, and I also added it to the end of a line of text. Then I did them all the same, either own line or at the end of the line, and the results are still inconclusive in that I have no idea why the bottom one with the pictures is tiny, and fittingly so, but the others with what looks like the same length of text, and by that I mean the text goes all the way over and then wraps down to the second line, have such varying lengths.
I mean it looks "weird" and that's okay. It still works and was fun to try and use. I just feel like i must be missing something that would suggest to me what the length should be.