Hoping that Wendy will weigh in later, but I think you can take another reduction to 5.5U. Dose changes over 5U (and below 10U) are in multiples of 0.5U. At 6U, the limes you saw last night could still be the higher depot, since for larger doses, the depot can affect more than 4 cycles. However, it's also possible he has flipped a switch and wants to head lower in dosing.
How are you placed wrt monitoring? Can you monitor closely if you hold the dose and don't reduce?