I think they are numbers, more specifically showing device dimensions & others may refer to some formulas .

The Arabic notation for numbers as we know it now (1,2,3 ..etc) wasn't yet formed! i suppose!!

You will find most of the mentioned symbols in this image showing the developing of numbers

http://en.wikipedia.org/wiki/Arabic_numerals#mediaviewer/Fil...

Note: (in the image the development in vertical, first line lists numbers from 1 to 10)