Explaining 05-19 (2020):
MSC (Maritime Safety Committee in IMO) approved the 05th amendment to the IMSBC Code in 2019. (05-19) and it became available (as a recommendation to use) in 2020, anticipating its envisaged official entry into force on 1 January 2021.
Next edition will be 06-21 (2022). (Provided Covid-19 does not mess up scheduled meetings too much)