宽度,cm:[[Length inch]*2.54]——使用变量表达式([[variable]*value])显示固定文本(宽度,CM)。It is important to note the additional set of square brackets when using formulas with variables.
宽度,cm:[Length]——使用数据字段表达式([datafield*value])显示固定文本(宽度,CM)。Notice the single set of square brackets is required for data fields and formulas.