I don't know about Aegisub, but if those are .ass subtitles like I thinkthey are, then you can actually just open the sub file up in Wordpad and change the font size there.
...or by "stretch/shrink" do you mean something else?
So... what are you saying? The picture doesn't really help much. What do you mean by "normal" and "stretch"?
Stretch as in make the words bigger? Stretch as in make the words fill the length of the screen? Stretch them how?
And... I don't even understand what you mean by "normal." If you mean you're trying to get rid of the karaoke effects, then you can also do that in Wordpad. (It'll just take a lot of time.) But I don't think that's what you mean by "normal."
First of all make sure your script resolution matches your video resolution.
\fscx<percent> - Font scale in X axis
Sets the font scale for the X (horizontal) axis. Parameter should be in percent form. This is different from simply adjusting size using \fs because \fs will use font hinting to determine best looking adjustments, especially for small sizes. Also, \fs will only accept integer parameters. If you need to, for example, transform scale (with the \t tag), use this instead of \fs, as \fs will behave strangely and not smoothly. e.g.:
\fscx150
(makes the text 50% wider)
\fscx33
(makes the text have roughly a third of its original width)
[edit]
\fscy<percent> - Font scale in Y axis
Same as \fscx, but for the vertical axis.
Use as such:
type {\fscx190\fscy103.75} at the start of the line to play around with text
