Translations:Expression Manager/49/en
From LimeSurvey Manual
EM controls how most of the advanced question options work. These control aspects like min/max numbers of answers; min/max individual values; min/max sum values; and checking that entered values match specified string patterns. You continue to enter those advanced question options as usual. However, now any value in one of those fields is considered an expression, so you can have min/max criteria with complex conditional relationships to other questions.