Does spirit guardians cover underground of the caster [duplicate]

Clerics can cast the following 3rd level spell:

You call forth spirits to protect you. They flit around you to a distance of 15 feet for the duration. If you are good or neutral, their spectral form appears angelic or fey (your choice). If you are evil, they appear fiendish. When you cast this spell, you can designate any number of creatures you can see to be unaffected by it. An affected creature’s speed is halved in the area, and when the creature enters the area for the first time on a turn or starts its turn there, it must make a Wisdom saving throw. On a failed save, the creature takes 3d8 radiant damage (if you are good or neutral) or 3d8 necrotic damage (if you are evil). On a successful save, the creature takes half as much damage. At Higher Levels: When you cast this spell using a spell slot of 4th level or higher, the damage

Let’s say the caster is in the second floor and he casts spirit guardians. He mentions his ally next to him to be unaffected by it. Now, directly below him, he has two other PCs waiting. Since he can’t seem them, he cannot say that they are unaffected by the spell. Moreover, the spell has a radius of 15ft, so they are within the range.

Will the players in the bottom floor be target by the spirit guardians, or it will be limited to 2nd floor creatures only ?