Fractional Participation rate and blocks behind

[AgeManning]

I was playing around and saw:

The participation rate is said to be 100%, but its more like 99.6. Seems we are losing some decimal points here.

Also the blocks behind goes negative. This shouldn't be the case. The negative case should still register 0, but curious about the logic there as to why we get negative. I guess different clock times between client and server?