Out of five pregnancies my waters only broke spontaeneously once. So it was more like 20% for me.

I was fast asleep and I felt/heard that "POP" and I flooded my bed. Called DH cause he was at work and was busy stripping the bed and putting on washing when he got home at 2 oclock in the morning.
It really was hopeless trying to soak it up too cause although I totally drenched the bed I went still through about 3 prs of pants before I had even left the house. I ended up walking into maternity with a towel between my legs (I was sitting on 3 rolled up ones in the car too) and the dippy women behind the desk said "have your waters broken?" "um no love towels, are the new black!!"

Good luck but I wouldnt stress too much about it, its only water it can be washed/dried out