Don't forget that a circle does a very specific thing: it keeps magical energies out. And it does so absolutely. It's not like the better you are at drawing circles, the more energy you block out. A ghost or any other spiritual being can't just push through a circle if they are powerful enough, that's not how it works. So assigning a number to a circle like that doesn't make any sense. Rolling for it with lore doesn't make sense. If someone told me "draw a circle to protect you from magical energies", I don't need to increase my lore to know that.
What the lore could help with is to correctly identify the threat. Is this normal fog or something magical? If you're successful, you know it's magical and you decide to put up a circle. In this incident, the salt might be an aspect, but it might just be that it's buying out of a compel that chalk might not stick to the Walmart floor.
On the other hand, a circle is incredibly brittle to anything physical. A supernatural being with any physicality to it will simply walk through it and break it, making way for its supernatural part. For those, you would need a block, a ward, a full blown containment ritual, however you may want to call it, anyway.
Not to mention, it's not really interesting inside a circle. Whatever was after you is still out there and will probably just go after someone else. If it's a ghost, maybe they'll just inhabit someone or something and cross the circle and go from there. Maybe the circle is just your way of doing a concession, you're taking yourself out of the conflict with the spirit being.