以上, 以下, and 未満: whether a quantity includes its boundary
Compare inclusive 以上 and 以下 with exclusive 未満 in weight and height conditions, then identify the scope of a prohibition.
From a value and up to a value
以上, read いじょう, includes the reference value and larger quantities. 重さが三キロ以上です。 means a weight of three kilograms or more.
以下, read いか, includes the reference and smaller quantities. 重さが三キロ以下です。 includes exactly three kilograms. These ranges overlap at the boundary three.
Less than the boundary
未満, read みまん, excludes the reference value. 重さが三キロ未満です。 does not include exactly three kilograms.
身長が百二十センチ未満の子どもは利用できない。 says that children under 120 centimeters cannot use the facility. A height of exactly 120 does not meet that under condition.
Negation and the prohibited range
この箱には三キロ以上の荷物を入れないでください。 requests not placing loads of three kilograms or more into this box. Exactly three is within the prohibited range.
First check boundary inclusion, then whether the sentence permits or prohibits. Falling outside one under condition does not establish satisfaction of every other use condition.
Does 三キロ以上の荷物を入れないでください。 prohibit exactly three kilograms too?
Show the answer and why
Yes. 以上 includes the three-kilogram boundary, and the request prohibits loads in that range.