Why is the part going down along the x-axis and not rotating inwards on the y-axis?

Okay so the arm goes up and the lower arm or the elbow bends accordingly but then when I try to get the upperarm or the shoulder to rotate along the y-axis it goes back down along the x-axis. So for some reason despite me telling it to rotate inwards along the y-axis it goes down on the x-axis. And before you say something like "Use math.rad pl0x" I already defined rad to be equal to math.rad.

local num = 0
local p = game.Players.LocalPlayer
local char = p.Character
local rad = math.rad
local hum = char.Humanoid
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----RightElbow.C0 = RightElbow.C0:lerp(CFrame.new(RightElbow.C0.p)*CFrame.Angles(rad(0),rad(0),rad(0),0.1)----
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local RightUpperArm = char.RightUpperArm
local RightShoulder = char.RightUpperArm.RightShoulder
local RightLowerArm = char.RightLowerArm
local RightElbow = char.RightLowerArm.RightElbow 
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for i = 1,100 do
       RightShoulder.C0 = RightShoulder.C0:lerp(CFrame.new(RightShoulder.C0.p)*CFrame.Angles(rad(72.58)
,rad(0),rad(0)),0.1)
       RightElbow.C0 = RightElbow.C0:lerp(CFrame.new(RightElbow.C0.p)*CFrame.Angles(rad(41.64),
rad(0),rad(0)),0.1)
 wait()
end
for i=1,100 do
    RightShoulder.C0 = RightShoulder.C0:lerp(CFrame.new(RightShoulder.C0.p)*CFrame.Angles(rad(72.58),
rad(0),rad(0)),0.1)
        RightShoulder.C0 = RightShoulder.C0:lerp(CFrame.new(RightShoulder.C0.p)*CFrame.Angles(rad(0),
rad(-3.2),
rad(0)),0.1)
wait()
end