I got a tripple beam balance scale now. No directions and have a /some questions. I have some photos. Notice the sliding black weight on back of beam. If slid to the right...I can weigh more weight. What I do not know then is how to calculate the weight. There seams to be no marks on that beam it slides on? This is all new to me. If anyone can point me in the right direction....please do. thanks Capt,n