Br.annatc

Hi all! Long timer lurker, first time poster. My 309 visa was granted in Feb (Applied Oct '18) with a 'For first entry, arrive by 06 Jan 2020' detailed on the grant letter. My partner and I travelled to Aus in March for a month holiday and came back to the UK, no problems. In trying to sort out job apps etc, I accessed my VEVO today for a potential future employer. On the VEVO it states: 'Enter before date: 06 January 2020', despite the fact we've already made a first entry. Is this date set in stone? Will I be penalised for not having arrived by 06/01/20? We aren't planning to move until the last week of Jan 2020 I was under the impression that after making a first entry you could come and go as you please? Any help would be appreciated, or if anyone knows the best department to contact that would be helpful also! TIA Breanna