Tensioning the Long Belts

Good afternoon!
I read this support in the support section:
 

Tensioning the Long Belts  

Move the extruder to the center position. Tighten the screws on the axis block using a 1,5mm Allen key.

 
The question is - how much need to tighten the bolts?
How many turns?
I understand that the bolts rest against the rubber?
Just on the senses, they are not so tight in the new printer ;-)
 
And I correctly understand that these bolts need to be tightened from two sides of the printer?
 
Thanks in advance for the advice!