The amount of Points is increased with 5 for every burst after a miss or from the beginning.
First burst: 10 Points/Bubble
Second burst: 15 Points/Bubble
Third burst: 20 Points/Bubble
Fourth burst: 35 Points/Bubble
So if you have four bursts with no bubbles falling into a Cauldron and you burst three bubbles/burst, that gives you 10*3+15*3+20*3+25*3 = 210 Points.
That is almost zero scoring! You want to burst as few bubbles as possible, but continuously to get green Spiders or yellow Spiders. Every time a bubble hits a yellow spider your score increase, you see, and the green Spiders doubles the bubbles.
Minimum Score for falling into a Cauldron: 100
Maximum Score for falling into a Cauldron: n/a (At least 8000+ recorded.) :)
The Score doubles whenever a bubble hit a yellow Spider before falling into a cauldron.