Negative Calendar spread when in Contango, why????

Hi Guys, A quick question which puzzled me this morning. Basis: Spot price - Future price Calendar spread: Future price (of a more distant maturity) - Future price (of a more nearer maturity). I understand that contango is when future prices are higher at dates further in the future. => So, contango: negative basis. OK But, why do the curriculum says that the calendar spread is also negative (for me it should be positive). Regards,

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