System plugin 'b' parameter?

I just replied to somebody who wanted to move the MUI header background image behind the text - which I'd done before after grabbing some code from a thread on here to move a control around. That code takes the form:

System::Call "User32::SetWindowPos(i, i, i, i, i, i, i) b (Hwnd, Hwndafter, X, Y, W, H, Flags)"

But having read the System plugin's documentation quite a bit recently, it occurred to me that I haven't the foggiest where that 'b' is coming from. It doesn't appear to be documented.

Changing the code around to..

System::Call "User32::SetWindowPos(iHwnd, iHwndafter, iX, iY, iW, iH, iFlags)"

..seems to have the exact same effect.

So my question is: What purposes does the 'b' parameter serve - is it any different from specifying the values directly?

there is no such thing as a b

a BOOL is 4 bytes=i
a bool is 1 byte=&i1 (in structures)

okay, so presumably that 'b' should be an 'i', if anything; the rest of the thing, then... does the separate (value, value, value, etc.), which would be the 'return' as far as the System docs seem to be concerned, essentially just get used as the input values?

I don't know where it originated originally.. could have been..

or

yes, you can specify the input parameters several times