Discrepancy between Weeknumber i nOnscreen Gantt Chart and print/print preview

[deesloop]

We are producing a Gantt chart for a project.
The project is set to Start 06/03/2017


So week 1 in our heads is obviously week commencing 06/03/2017

However some prep work needs done 8 weeks before the project starts in earnest
So we have a task 1a that starts 6 weeks prior to 06/03/2017 eg 09/01/2017

When I add this task the weeks are renumbered so that that week 1 starts when Task 1a starts (09/01/2017) rather than what the project start date is set to (06/03/2017).

However when you preview/print it week 1 is indeed as per the project start date (06/03/201) and task1a is shown to run from -8w to week1

Project 2007 doesn't display this behaviour. On screen shows W1 as being 6/3/2017 and the print/preview matches. The issues is for Project 2013 and have been tried on 3 or 4 machines all displaying the same issue.

How do we get the Gantt chart to match the print preview/printout.

I've attached 2 images.
One is a screen shot from within Project
The other is a screen shot after having printed the doc to PDF - however the physical print out matches this.