shares on issue: 339.78 million, from
http://www.asx.com.au/asx/research/company.do#!/MSB
so multiply by 7.53% and there's your answer: 25.6 million shorted.
( just a rough double check, 10% would be 33.9 million).
As noted by other posters, it is quite possible that the shorts are being issued as part of a wider and sustained strategy to get cheap shares.
BTW there aren't all that many shares on issue, which is why the company has the flexibility to offer shares as part of a deal.
To work out how many shares a company might have in the future check the anns for the last options issued, they always list the total number of options. Options which have not yet been exercised, aren't yet included in the total shares on issue.
cheers
(20min delay)