I have a question about the controls built into this enlarger - Agfa C66 (which looks like a Durst 605 - except for added control panel on the back of the baseboard). There is a probe with a dial with a number scale from 0 to 7 for Sensitivity. There is a number dial for exposure with a scale from 2 to 100. My question is - are these numbers seconds, or some type of exposure units?? I have done a number of test runs comparing to a stop watch, if these units are seconds, then the times are way off and not by a constant amount. Changing the probe settings does not seem to be linear either. The instuction sheet is very short on info about using the enlarger and refers to a test using a colour slide. Would appreciate any insight into using the probe and exposure controls - I was planning on using this for B/W work.