[jQuery] [help] Math + Checkboxes

[jQuery] [help] Math + Checkboxes


Hi there. I'm not very good with Jquery and JS yet, so I'm having a
bit of a problem trying to achieve this.
What I need to do is explained here:
http://ignacioricci.com/alphas/jquery-issue.gif
And here is my actual code:
http://ignacioricci.com/alphas/jquery-issue.html
Is working in a way, but it's buggy. This bug is explained in the gif
image.
Thank you for your help,
Ignacio