[Utah-astronomy] Club DOAA SSP - how to use?

The club lent me their old DOAA stellar photometer.  http://members.csolutions.net/fisherka/astronote/Photometry/DOAA_SSP.JPG - but there is no manual. Its current successor is the Optec SSP series: http://www.optecinc.com/astronomy/ssp_main.htm  For the older model, to confirm, is the brightness unit value simply the range knob number times the number on the indicator dial (1..100)? What is the indicator scale for 1..25 for? Thanks, Clear Skies - Kurt