[cosmic_ape]

Isn't it strange that the periods mentioned are integer multiples of days?

Don't known much about astronomy, but day as a unit of time is just a constant specific to our particular solar system. I guess a function of the sizes of the sun and the planets here. There should be nothing special about it. To think that 500M light years away there is something that has similar time proportions to be observed here as periodic is amazing by itself.

[qayxc]

The period is 16.35 +/-0.18 days [1] so it's not exactly 16 days. The unit days is just the next best convenient unit to use for this range of time scale. 392 hours +/- 4 hours just isn't as intuitive as 16 days.

So the period is neither an integer multiple of days, nor exactly the same each time. There's some small variance involved - about 1%.

[1] https://en.wikipedia.org/wiki/FRB_180916.J0158%2B65