The 6225 has 800 MB of internal storage dedicated to user data.
The number of measurements or TSV files that can be saved on the 6225 depends on the measurement length. For 20 meter measurements, the binary measurement file is about 4.5 MB, while the TSV file is around 8.5 MB. For 50 meters, the binary file is around 13.5 MB, and the TSV file 26 MB.
Therefore, the Luna 6225 can save both the binary file and TSV file for about 60 20-meter measurements, or 20 50-meter measurements.
Note that the user cannot do anything with the TSV file on the instrument itself, so it is only stored on the instrument temporarily until the user exports the files to an external USB drive to be moved to a PC for analysis.