SQO1/SQV1 - can't work this out

Ok have a report that deals with AFS items...one is in SQO1, one is in SQV1. n SQV1 the report has tables EKPO, EKKO and EKET in SQ01 the table joined are EKPO and EKET.

Both reports have the same list and output fields however when I run the SQ01 report it will list all the materials on a given PO, whilst the SQV1 will only list one material?

Any ideas why this is the case, thanks