About skip voxel at ________ due to lack of events

[HibanaSledge]

Really appreciated for your code in DEVO.
While I try to do the evaluation using the mvsec dataset, I found that the terminal will return information like below:
skip voxel at 1504915781.627514 due to lack of events!
skip voxel at 1504915781.7243729 due to lack of events!
skip voxel at 1504915781.8212318 due to lack of events!
skip voxel at 1504915781.9180918 due to lack of events!
skip voxel at 1504915782.0149508 due to lack of events!
skip voxel at 1504915782.111811 due to lack of events!
skip voxel at 1504915782.20867 due to lack of events!
skip voxel at 1504915782.3055289 due to lack of events!
skip voxel at 1504915782.4023888 due to lack of events!
skip voxel at 1504915782.4992478 due to lack of events!
skip voxel at 1504915782.5961077 due to lack of events!
skip voxel at 1504915782.6929667 due to lack of events!
skip voxel at 1504915782.789826 due to lack of events!

I have asked the search engine and it said it is normal, but I am a bit doubt about that, could you explain this to me? Really appreciated!