Completely agree - any scale back should be on the amount held...

Completely agree - any scale back should be on the amount held on the record date (or if you sell after the record date, the lower amount on the close of the SPP).

They say they have done it in accordance with the terms of the SPP. This is what the SPP says:

When determining any scale back or rejection of applications, the Company may take into account a number of factors, including the size of the applicant's shareholding, the extent to which Eligible Shareholders have sold or purchased additional Shares after the Record Date, whether the applicant has multiple registered holdings and the date on which an application was made.

I'm assuming it is subject to pro rata then, using some minimum allocation, and not the amount subscribed.

ASX had proposed a listing rule that required full details of any scale back that wasn't on a pro-rata basis. I think it is a good idea.