OpenCV 2.4.5.0 Documentation gpu::subtract says "const GpuMat& b to be ADDED to const GpuMat& a"

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In the OpenCV 2.4.5.0 Documentation on docs.opencv.org, I was looking up the parameters to be passed to the function gpu::subtract(). Unexpectedly, it states for parameter GpuMat& b

void gpu::subtract( const GpuMat& a, const GpuMat& b, GpuMat& c, const GpuMat& mask=GpuMat(), int dtype=-1, Stream& stream=Stream::Null() )

const GpuMat& a     First source matrix.

const GpuMat& b     Second source matrix, TO BE ADDED TO 'a' . Matrix should have the same size and type as ``a`` .

Does this really mean that the second GpuMat will be ADDED to the first (even though this is supposed to be the gpu:subtract()-function). Or is this a type-error?

(the parameter-declaration written with the function gpu:add() has the exact same words as the gpu::subtract()-function, suggesting to me that this may indeed be a typo... I still would like to know for sure though, and otherwise bring this to the attention.