The length of the message screen is not equal to the width of the message box. I'm not sure why it's set up that way, myself.

The in-game font uses monospaced fonts, and can hold 50 characters per line, by my count. A picture should help:



Of course, it's obviously lower with a picture - when that happens, the character limit is 38!



As a general rule, keep all text before the C in the "Cancel" button.
If you're using a picture, keep the text before the right edge of the OK button.

Obviously, this won't always work, but it'll keep you from having to redo much - you might have one letter over the limit sometime, or you might have a lot of space left on that line. You could always do a character count in Word if you're worried about a particular line.

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Remember that, in normal, proportionally spaced fonts, the letter "i" takes up less space than an "m". 10 of each letter:

iiiiiiiiii
mmmmmmmmmm

In a monospaced font, "i" and "m" take the same amount of space:

iiiiiiiiii
mmmmmmmmmm


So that's the reason for this whole problem.