From what I understand, the minimum clock resolution is the smallest atomic clock interval recognized by the J2ME VM. As an analogy, the minimum clock resolution of your watch is 1 sec. (assuming you have a Quartz watch).
Here's the relevant portion from JTWI 1.1 spec.
In a compliant device, the method java.lang.System.currentTimeMillis() must record the elapsed time in increments not to exceed 40 milliseconds. Also, at least 80% of the invocations must meet this time elapsed requirement.
In other words, two immediate calls to System.currentTimeMillis() should not have a gap of more than 40 milliseconds 80% of the time.