Advanced Portfolio - even more problems

[dunbrokin]

Back to BBBY of which the client holds 523 in their portfolio. The basis of
this holding in NZ$ today is around NZ$45,750. Now if I go back to look at
the basis value of the holding in  December 2014, then the value is
NZ$40,125 - no shares have been bought or sold. So, this basis has changed
by NZ$5,000 (as in increased) at a time when the value of the NZ$ against
the US$ has fallen from 1NZ$ = US$.76 to 1NZ$=US$.66. What am I missing
here?