The caster level (CL) is set by the creator of the potion, as per Brew Potion:
When you create a potion, you set the caster level, which must be
sufficient to cast the spell in question and no higher than your own
If you don't know it, the general rule of thumb is to use the minimum caster level required to cast the spell (as that's the minimum level it could be created at). For Cure Light Wounds, that is CL 1. Thus a normal potion of Cure Light Wounds heals 1d8+1.
It is possible for someone to create a CL 5 potion of Cure Light Wounds, though. That potion would have a higher value, which is explained on the Potions list.
The price of a potion is equal to the level of the spell × the
creator's caster level × 50 gp. If the potion has a material component
cost, it is added to the base price and cost to create.