From the manual, page 24:
Both Flex and Static machines can handle 16 or 24 bit/44.1 kHz wav/aiff files, either in mono or stereo.
You can choose whether to store internally at 16 bit or 24 bit resolution for both the Flex sample slot list and the recorder buffers, in the PROJECT>CONTROL>MEMORY menu (manual, page 39).
One minute of stereo, 16 bit, 44.1 kHz audio occupies about 10 MB of RAM. That’s about 0.17 MB/s.
So 64 MB default Flex slot RAM gives you 380 s (just over 6 min) of sample storage at the above settings.