Hello 
I would like to clarify a few issues.
1. What exactly means - Buffer size per channel: 256
Does this mean - if we have - Sampling rate: 16MSPS, the oscilloscope can remember and display a continuous signal only 256 points -. ie 256 / 16MSPS = 16 E-6 sec.
2. Can an oscilloscope to record and read waveforms on a memory card?
 
Thank you.

1) correct
2) yes, the xmegalab can store waveforms on the sd card in the following formats: BMP, CSV and WFM. The WFM is the internal format which also saves all the scope settings.