My chamber level is 8 and my equipment level is 3. My active mine time is 58 min and 30 sec. First I did 8 x 5 and got 40 minutes from the chambers. Then I did 40 x .3 and got 12. 40 + 12 = 52 then I added the 5 min you start with. That equals 57. Where does the other 1.5 min come from?
i seem to be coming up with 58.5 minutes based on my experience, each upgrade gets you 30 seconds per chamber so should be 45 in chambers 4.5 minutes each upgrade X 13.5 minutes. so you should be at 45 minutes in chambers and 13.5 minutes in upgrades getting you 58.5 minutes all together