Problem about timestamp

[shandwg]

Hi,
Thank you for coding the driver for R2000. I have modified the scan_frequency to 20 HZ, and samples_per_scan was 1440, when I run the driver, I use the ros command "rostopic hz /scan" to catch the frequency of the laser, the frequency is similar to the frequency as I set before, Then I use the command"rostopic echo /scan", and i subscribe the timestamp of two scans to get the interval, I found that the interval didn't correspond to the frequency i set before, I would really appreciate if you can help me on this.

Regards.
Gengwang