[Need Help] What does it tell you?

[adoi]

This is an S-M-C Takumar 28/3.5 M42 lens.
I don't understand the numbers on the second row from the bottom. They appear to be numbers that were taken from aperture steps. They must have some kind of use for us, if not why would they bother to put the numbers there. Anyone care to enlighten me? Ow yes, another one, the "R" symbol on that particular row, painted in orange, what does it mean? Thanks in advance...

[fish4570]

They are for depth of field reference, and determination of hyperfocal distance for a given aperture.
Look at f3.5 on your reference photo. You will notice two of them, right? Look at the distance scale above each f3.5 marking. If you shoot at the distance at which your photo shows, your subject will be in focus from 3 meters to infinity.
If you shoot at f11, your subject will in focus from 1.5 meters to inifinty ...

[Scheimpflug]

... and the "R" is the infra-red focus point. Since IR is of different wavelengths than normal visible light, the lens focus has to be adjusted when using IR film.

The typical technique is to focus normally, then look at the lens and see what distance it is focused to. The focus is then adjusted so that this distance (what was previously aligned with the orange diamond) is aligned with the "R" marking. It will appear out of focus to your eye in the viewfinder, but will be focused correctly for the IR-sensitive film when you take the picture.

[adoi]

Thanks a lot fish4570! That really enlighten me! Now I really understand the function of those numbers. Thanks again fish4570!
Oww...do you happen to know the meaning of the "R" symbol?

[adoi]

Ohh wow! Scheimpflug, thank you very much! If you hadn't explained it, I guees I'll never understand that until the rest of my life... hahahha!
Pardon my excitement, I'm still very new in using old manual lenses, I'm one of those digital kids. Cheers!

[Farside]

You will find hyperfocal setting useful if you do street photography. Simply set the lens on say f11 and set the focal distance to 2m - everything you see will be in focus from 1.2m to infinity, so no need to touch the focus, which saves time in point and shoot street use.
This assumes the light is good and your sensor (or film) isn't noisy at 400 or 800 ISO. The results aren't usually as pin-sharp as the lens is capable of being, but are often perfectly good enough to use, if something unique happens in front of you unexpectedly.