Account Assignment Reference Transfer - Partial amount

Hello,

my client wants to transfer a security position from one AAR to another. The point is that not the whole position should be transferred only a partial amount. E.g. the current position is a nominal value of EUR 1.5 Mio. and only EUR 1 Mio. should be transferred. In the tx valuation class transfer TPM15M I have the possibility to define an nominal amount but I don't see this possibility in the AAR Transfer transaction.

Is there a way to transfer a partial amount within the AAR Transfer transaction TPM28 or how could this requirement be realized? Any help is appreciated.

Kind regards

Robert