I am trying to read a technical 2D CAD drawing of a machine screw.
Here is an image of the PDF:
I added the blue arrows to highlight instances of confusion.
What does it mean if there are two figures provided for the same dimension?
I thought that maybe these two figures referred to a "tolerance" of possible values (that is, a "minimum" and a "maximum"), but I'm not confident in this theory because, in all four instances, the greater number is on top (which seems counterintuitive to how a range is typically expressed).
I tried looking up "ASME B18.6.3" to see if it contained any hints, but it costs $107 to view this document.
Also, if no units are provided on a blueprint like this, how do I know if the figures are measured in inches or millimeters?
Fastenal is a U.S.-based company, so I expected that they use the imperial system, but the figures contain odd numbers, so, on the other hand, they might be using the metric system.