The Diaspora SRD says
If you exceed your opponent when you make a defensive roll that does not have any effect other than being a successful defense, you don't get shifts. Instead, for every three by which you exceed the attacking roll, you generate spin.
While it's own sidebar says
attacker and defender roll dice and add skill. Attacker result - defender result = shifts. If negative 3 or lower, defender gets spin.
So, can you generate multiple "spin" on a successful defense, or only one. If you can generate multiple can you use multiple spin on the same roll?