Bare numerals (e.g. two) seem to be ambiguous between two readings: the exactly and the at least reading. We present an ERP study that explores this issue. We show that the pattern of the ERPs elicited by critical nouns in sentences with unembedded bare numerals depends on the participant’s choice of the reading of the numeral. For those responders who consistently apply the exactly reading in their truth-value judgement, sentences that are true only under the at least reading are associated with a sustained negativity effect compared to sentences that are true also under the exactly reading. However, no such effect is evident for the responders who apply the at least interpretation. We argue that this result falsifies the exactly-theory of numerals and speaks in favor of the ambiguity account.