At 60% RH, the lumber's surface will dry to about 10% MC, but no drier. It will take many weeks to get that dry throughout the piece. So, the surface will be at 10% MC, but it is impossible to get the surface any drier. The core will therefore be wetter.
To achieve 7% MC lumber in a reasonably short time, you will need to use 25 to 30% RH or a bit lower at 110 F. That will give 6% MC at the surface.
As a rule of thumb, at 110 F and 30% RH, you might, on a good day, achieve with 4/4 oak about 1/2% MC loss per day. For 8/4 less than 1/4% MC loss per day. Why so slow? We are waiting for the water to move out of the wood and not for the air to scrub the water off the surface. So, the size of the compressor is not the issue at these low MCs, but rather how fast the water moves out of the wood. Temperature is a big factor at the end of drying. If the surface MC and the air's moisture are the same (such as 60% RH and 10% MC), then no drying will occur.
A complete listing of RH and MC values is given in many documents, including pages 16 & 17 in DRYING HARDWOOD LUMBER. (Download here at WoodWeb.)