Looking at more log outputs,
looks like during the early period of testing, OptimalF is 0.0 and then became 0.103.

Test period starts from 13-06-12 (12th of june 2013)
[118304: Wed 13-06-12 21:30] (1611.50)
OptimalF 0.000000

Lookback period doesn't seem to affect optimalF, as expected
End of lookback period
[118384: Fri 13-06-14 14:30] (1636.20)
OptimalF 0.000000

OptimalF becomes non-zero only on the 24th of june 2013
[118666: Mon 13-06-24 19:30] (1577.40)
OptimalF 0.103000

I tried to look through the manual, but there is no indication that OptimalF changes over time.
Am I missing something?

Thank you