What does "Shocks/Chills enemies as though dealing X% more damage" mean?

Status ailments in Path of Exile are based on the damage of the hit. For instance, in your case:

• Cold damage always inflicts chill. Chill slows all actions of the affected target up to 30%, based on the cold damage of the hit. The base duration is 2 seconds.
• Shock causes the affected target to take up to 50% increased damage from all sources, based on the lightning damage of the hit. The base duration is 2 seconds.

You can read up on the way damage calculations are made here:

• Shock
• Chill

Essentially, the "Chills/Shocks enemies as though dealing X% more damage" will calculate your skill's chance to chill based on an increased damage modifier of your damage dealt. Take a hypothetical scenario where you deal 100 cold damage to the enemy. A level 1 Ice Shot has a "Chilled enemies as though dealing 100% more damage". Instead of your chill effect being based off 100 damage, it would instead be based off the base damage "as if it was 100% more damage", thus making your chill effect based off "200 damage", despite you not dealing that much.

Basically, it increases your threshold to apply the chill/shock in the first place, since a higher damage value is being used in the calculation of that effect being applied.

They way status elements proc is if you successfully roll a status proc based on your the chance to inflict status, and the enemy fails to resist the status, or if you inflict a critical strike.

Status effects, such as shocked which allows you to deal up to 50% more damage, are based on the amount of damage you do. The higher the damage you do when you proc shock, the higher the percentage of extra damage you will be able to have on a shocked enemy, with a minimum of 5% and max of 50%. The exact formula is shown below, where D is your total damage that can shock, T is is the enemy's ailment threshold (normally their max health), and M is the sum of the attacker's increases to the effect of shock (comes from X% increased effect of shock modifiers).

So, shocks as if dealing X% more damage modifiers help increase the effectiveness of you shock procs, similarly to X% increased effect of shock modifiers.

See here for a more in depth explanation.