Normally this is obviously correct, but in this case, we have to consider how tall the characters are. As a DM, I would rule that if any part of the character (their actual person, not including, say, the reach of the sword they’re holding) is within the 30’ circle, or could be if they actively collaborated with the cleric using free actions, then the bless would affect them.
There’s also a few definitions we need to talk about:
if the cleric (we’ll call them Carl) is 30’ in the air, that is understood to mean that if the spell holding them up there fails, they will fall 30’. By the same token, a character 0’ feet in the air can only fall 0’. We can infer that Carl’s feet (or the bottom part of the PC, at any rate) are 30 feet in air.
we consider Carl to be in the center of the 5x5 grid square in the plane A formed 30’ above the flat terrain.
the “allies are 20ft away” part is a bit too fuzzy for this to work (how many allies? which ones? they can’t all occupy the same grid square unless they’re tiny), so we’ll have to make some calls here. Let’s just consider one ally, Alice, who is 20’ away.
We consider Alice to be in the center of her grid square, in the plane T formed by the flat terrain.
When we say Alice is “20ft away” from Carl, we mean that a perpendicular line drawn through the cleric intersects with T at the center of a grid square in A–we’ll call this square C(T) and Carl’s square at current altitude C(A), and the center of C(T) is 20’ from the center of Alice’s square A(T). Visualized as a battle grid you would have C ◻◻◻ A in plane T, with 3 empty squares separating them. On a physical table, Carl would also probably be standing on a little platform or a d6 to indicate altitude.
“Range: 30ft” 30 feet from what? Definitely not Carl’s god, they’re probably not even in the room. Maybe we mean 30ft from Carl’s 3rd chakra, or maybe it’s just 30ft from any part of Carl’s person. That seems easier, let’s go with that one.
Based on some anthropometric data I found very quickly, the average human woman has a vertical reach of about 77 inches or 6’ 5". That’s naked, and she’s probably wearing boots, let’s add another inch for the soles so 6’ 6".
We can give her a little bit more of an advantage as well; the shortest path between Alice and Carl is a straight line following the radius of the sphere, so she could “lean in” a bit with her arm to get closer. She can’t go a full 45 degrees without falling prone though, so this only adds a little. Without a posable figure and a 3d model of the space in front of me I couldn’t tell you how much she could reasonably add by pointing her body and hand at an angle, so let’s just call it 2 more inches and keep measuring vertically.
We’ll call the apex of her fingertips at 80 inches above T a new plane F, and A(F) is the point where she touches that plane with her fingers.
Now we get to actually apply the Pythagorean theorem. It’s a triangle formed by the points (C(A) -> A(A) = 240") as leg 1 and (A(A) -> A(F) = 280") as leg 2. The hypotenuse, then, is 368 inches.
30ft is 360 inches. Is 80 inches of Alice enough to put a fingertip through any part of a 30ft sphere around Carl’s feet?