This is a scaled claim that pays (NTS-10)*0.10$ with NTS the number of named tropical storms originated in 2007 in the Atlantic Basin. The mean of the number of named storms is 9.6. 2005 was the record year with 28 named storms. If there would be 10 NTS or less in the Atlantic Basin in 2007 the claim pays $0. If there were 20 or more named tropical storms the claim pays $1. The names and discussions of the tropical storms can be found on http://www.nhc.noaa.gov
I will substitute an appropriate authoritative source in the event named storms aren't available from the source in the claim.
Now, by my calculation, there are seventeen events, 2 of which are depressions-not storms. That would suggest a judgement of $0.50. I'm going here by the example of how the number of named storms for 2005 was arrived at in the wording of the claim.