Weed Eater One

My weedeater one is two years old. The engine faileds during the first year, and briggs paid for the repair. They had to do a major rebuild. I love the unit, but it always has seemed to use a lot of oil, and I have trouble reading the dipstick. I am very careful on this, but my question is because there is always oil on the dip stick when I try to read it, do i go by the larger quantity drop at the bottom or do I read it some other way. I have had lawn mowers all my life and I am 69, and I have never had trouble reading the dipstick. Each time I mow I have to ad oil and I am not really sure of how much to ad as it is so difficult to read the stick. I know you are not supposed to over fill, but again, I am frustrated, as I can always tell when it is low, because the engine starts to perform badly. As soon as I put oil in it runs like a top.. I have an old bolens mulching mower that I have had for 20 years and only changed oil once, and never have had to add any oil. It is a briggs motor as well. HOpefully you can help me out I have included a picture taken a few minutes ago so you can see what I am talking about. There is the larger amount at the end, but oil reads up to the second one and looks to be full. I don't want to over fill, so hopefully you can help

Thanks
Len Johnson