浮動小数点数
=ROUNDDOWN(1.0-0.9,1) = 0.1
=ROUNDDOWN(1.1-1.0,1) = 0.1
=ROUNDDOWN(1.2-1.1,1) = 0
=ROUNDDOWN(1.3-1.2,1) = 0.1
=ROUNDDOWN(1.4-1.3,1) = 0
=ROUNDDOWN(1.0-0.9,1) = 0.1
=ROUNDDOWN(1.1-1.0,1) = 0.1
=ROUNDDOWN(1.2-1.1,1) = 0
=ROUNDDOWN(1.3-1.2,1) = 0.1
=ROUNDDOWN(1.4-1.3,1) = 0