Some addition:
The seed bonus points are calculated using the amount of time that you have a torrent seeding.
So if you are seeding even one torrent you will get seed bonus points (.5 for 1 hours seeding). This way even if there is no real upload traffic you are still being rewarded for seeding the torrent and keeping it alive.
Its a reward because you can exchange these points for actual upload amount thereby increasing your ratio.
You will know that you are getting SBP when there is atleast 1 near the upward facing green arrow at the top left of the screen.
"On the fly into traffic" means that when you exchange the SBP you will get the said amount of GB added to your total upload amount (100SBP - 1GB added to total upload amount, and so on.)