Symbol occurs in more than one context – only once defined

I don’t understand why I am getting an error for "K" but not let’s say "A" – and the slider is labeled with "Global`K"

ClearAll(Y, A, K, L, a)
Y(A_, K_, L_, a_) := A*K^a*L^(1 - a);

Manipulate(Plot(Y(A, K, L, a), {L, 0, 100},PlotRange -> {25, 3000}), {{A, 5}, 1, 10}, {{K, 225}, 200, 350}, {{a, 1/3}, 10^-2, 1})

Thanks!