at least evaluates as true if a statement is true for more than or as many as some specified number of episodes.
For example, given the following case fragment,
05 Feb 03 06 Oct 03 07 Nov 03 HDL [2, 5.5] 7.3* 5.6* 6.1* LDL 1.1 0.8 pending Trig 3.2 3.6 LipidDrug note 1 note 3
at least 3 HDL are high
at least 1 LDL is “pending”
at least 2 LipidDrug contain “note”