Confusion in numbering Popes John results from an error in the textual transmission of the entry on John XIV (983/984) in the Liber Pontificalis. This entry originally specified not only the duration of his pontificate ("VIII mens." = eight months), but also the duration of his ensuing imprisonment by Antipope Boniface VII, "per IV menses" ("for four months"). In the 11th century, some time after the pontificate of John XIX, this entry on John XIV was misread to be referring to two different popes John, the first reigning for eight months and directly succeeded by another John reigning for four months: