[probably a question] Cannot set the left margin to 0

[wsw70]

I tried to create a cell that would start on the edge of the page:

pdf.SetMargins(0,0,0)
pdf.SetX(0)
pdf.SetY(0)
pdf.Cell(0, 0, "QR")

I get this:

Where does the space marked in red come from?

Note: I guess that this is not due to the font - I changed its size but the gap stays the same. It would also seem that the gap is exactly 1 mm wide: