cfa635 bitmap fill

I'm making some tests with my new cf635, python and a 3th part library and I see a "strange" behavior with a bitmap "fill": I can set only 5 columns (of the 6 present every bitmap) to 1 (so black). But I don't know if it's a library problem or something other so, before spend time for nothing, I'm asking here for know if the 635 can fill a complete line with "black" (light on) squares or not.

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