Gunslinger Class: Valda's Spire of secrets

I have a question when it come to use of Magic as a second attack in gunslinger subclass Spellslinger. At this subclass level 3   

Level 3: Bang, You’re Dead!
You can use magic in place of guns.

and by level 5 in gunslinger class you get and extra attack. and then at level 6 in this subclass you get

Level 6: Spellshot
When you take the Attack action on your turn, you can replace one of the attacks with a casting of one of your Wizard cantrips that has a casting time of an action.

So my question with this is if by level 5 I get an extra attack, it is ok to use my guns twice, and it says by level 3 subclass I can use magic in place of guns. Why is it I apparently I not allowed to use my cantrip Finger Guns twice. Or any direct damage cantrip twice for this. I guess my mind is thinking like a Magic the Gathering player, RAW until something feels like it is telling you different.

Well, if it says "you can replace one of the attacks", then you can replace one of the attacks, not two.

"You can use magic in place of guns" sounds like the flavor text part of a larger feature that you have not quoted the actual rules part of.

Quote from wagnarokkr >>

"You can use magic in place of guns" sounds like the flavor text part of a larger feature that you have not quoted the actual rules part of.

This is exactly correct. The actual effects are twofold: You gain the Finger Guns cantrip and can add a Risk Die to the damage of Finger Guns.

I just tried to create a Gunslinger Multiclass and something odd happens. Whenever I try to add a Gun with a magical property the system flags that item as me not having proficiency in it's use. I think this is due to there being a difference between 5e and 5.5e firearms, but it still forces me to add the additional modifiers myself via customization.