The blnking dot under 0 indicates the exposure level is set to zero. When compensation is applied (using the +/- button), or the exposure level is changed using the command dial on the back to adjust the exposure (right-hand vertical scale in viewfinder), that blinking dot will move accordingly in +/- 0.3, 0.5 or 1 stop increments along the scale (depending on what steps of exposure you have set in custom functions).
The blinking dot also doubles up to show what custom function setting has been set for each of the custom functions, although interpretation of that is not (and never has been!) straightforward.
If the entire line of dots is blinking after loading film, it means correct film load has not been achieved.
The above is common to a number of EOS bodies e.g. 1, 1N, 1N-HS, 1V, 3...