Medium format film has the frame numbers printed right on the paper backing of the film itself. On the back of each Diana F+ camera, there is a red window that simultaneously keeps your film light-tight and allows you to see the film numbers on the paper backing.
Don’t worry if the numbers you see on the film are upside-down – that’s how they’re supposed to be!
Each film manufacturer has its own markings printed on the paper backing of the 120 format film. Some manufacturers use dots of decreasing size, dashes, or even arrows, in order to let you know when the next number is coming up.
The film should be wound slowly between each frame so you don’t overshoot the next number; there’s no rewinding when it comes to the Diana F+!