The length of the individual sounds matter, as well as some other factors.
I'm not an expert in acting, at all, just some natural talent for absorbing an emotion or the personality of someone (given the time) and be able to do it really good. Basically, an innate sense for emotion, even if I don't understand it.
Nevertheless, one of the things people get wrong is how laughter actually works. So let us go on a 5 hour long lecture on the history and specific functions of lau- I jest
If you laughed there, try to remember that sound you made.
While there are many different kinds of laughter, with my natural one starting with a big w h e e z e with much wheeze inbetween, in this case, I suppose there's no breath you have to work with.
Looking at the pitch curves and the length of the notes gives me somewhat of an idea of why it sounds off. A nice laughter often has very short bursts of voice, with different lengths inbetween depending on the person and exactly what. In general, you should listen to laughter samples to get an understanding as to how it works.
I'll provide something to start off with, the other person in these clips has consented to me sharing this. Intended to animate the entire clip but yet to decide a model for him so yeah
Not the purest samples, but this should give you a small idea over some of the way laughing works. (Clickable link!)
This is some organic laughter as well, I'm not the ultimate at acting laughter out. But yeah, in general, try to listen to organic laughter to find out its general functions to improve.
wish i could attach them wavs but i cannot so have this sndup link