A method for controlling a centrifuge blood component separation system for separating components of a blood product, the separation system comprising a centrifuge and a separation bag and at least one transfer bag. The method comprises selecting a nominal hematocrit value such that an actual hematocrit value is expected to be less than said nominal hematocrit; centrifuging a separation bag containing a volume of composite liquid so as to cause the sedimentation of at least a first component and a second component; transferring some of the first component to a first transfer bag; detecting time of passage of a red blood cell interface at a pre-selected location in the separation bag; and adjusting a predicted processing time based on the time of passage of the red blood cell interface.