The americans are the least stringent. API have the following ratings (in order from oldest to newest) : SG, SH, SJ, SL, and the new SM which deals with how well the oil deals with repeated cold starting.
So look for API SL or API SM on the side.
Europe have ACEA with grades that use a letter to donate the engine A=petrol, B= diesel, and C=Catalyst, followed by a number 3 or 5 to specifiy high performance.
So look for ACEA A3 or ACEA A5 on the side.
The Japanese have JASO that specifically do the MA grade for wet clutch and MB grade for dry clutch bikes.
So importantly look for JASO MA on the side (not aplicable to LE people ).
Finally when it comes to oil viscosity, the number before the W is the cold viscosity. You want this to be as low as possible so that the engine has an easier time starting. The number after the W is the operating temperature viscosity and this will be set by Benelli in the handbook. Dont play with it.
Someone else can bat on about Synth, semi syth, and mineral.
PS I would use Roickoil Synthesis 4 Racing. All the right certifications and being english you can ring them up if you need advice or reasurance (tell them [email protected] forced you into it).