chancePerHash=target/max numberOfHashesToWin=0.5/chancePerHash numberOfSecondsToWin=numberOfHashesToWin/hahesPerSecond
(0.5/(target/max))/hashesPerSecond
(0.5/(0x000000000f675c00000000000000000000000000000000000000000000000000/0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff))/1000000
=35689 seconds
About one block per 9.9 hours. Does this match your observations? I’m not totally sure about the math.