Ann: Form 603 and Disclosure under TP Guidance Note 20, page-5

It's because the more shares taken up in the Entitlement issue means the less shares our new shareholder has to sub-underwrite but that would mean they would get their additional shares to take them to 19.99% through a further(conditional)placement - so the minimum gross amount to be raised from the total equity issues is ~$105mil but if all shareholders took up their entitlements then the gross amount that would be raised is ~$119mil if the new shareholder didn't get any shares through sub-underwriting the entitlement issue as the additional placement would be triggered.
And, of course the Company wants to issue as many shares as possible as it could always do with an extra $14mil.