Please see
pic1.xilu.com/1/3118/6237719/e454c8bea5931d61f448220e6c6e3215.jpg

If Sagnac effect of a circle of light around the earth orbit
T = 0.628 s ,

then Sagnac effect between China and Japan
t = 0.628 s × 3000 / (1.5×10^8×3.14×2) = 2000 ns .

But the experiment tells us that t = 90 ns,
and it is considered to be caused by Earth's rotation.

If t = 0 ns , then T = 0 s.
But T can not equal to 0, but only equal to 0.628 s.

If t = 90 ns / 365, then T = 0.0000774 s.
But T can not equal to 0.0000774 s, but only equal to 0.628 s.

Someone says t = 0 or 90 ns / 365, but T = 0.628 s.
This means that either he did not understand physics,
or he does not know math.