Under extrusion?  

I would rate those prints as good enough for the first month.

Printers are shaken up in transit so during the first few weeks of use the printer will run-in and settle its parts together; then you will have to go over the basic maintenance checks, lubricate and recalibrate. Even if you got everything dialled in perfectly today, it would all need re-doing.

Better to settle, temporarily, for a basic working printer and get some useful printing done, make your early mistakes, establish a routine and generally get used to the process. Then when you do your one month service you can take extra care knowing the new settings on your now stable printer are likely to last for several months.

'Wrong Filament' means the name of the filament specified in the gcode file doesn't match what the printer thinks it has loaded.  Usually a user mistake.  Sometimes deliberate.

https://help.prusa3d.com/article/regular-printer-maintenance-core-one_829710

Cheerio

RE: Under extrusion?

That seems a bit worrying to me. What would ‘settle down’ after transit? 

I reloaded the filament and it seemed to get rid of the error. I then downloaded and sliced a Benchy - the only settings I changed were 20% infil and structural. Result is attached. My friend still says this is underextruding given the visible lines on the roof. Should I be increasing the flow rate?

I saw another post here saying decrease the extrusion temp by 10 and increase the bed by 10… could that help too? 

pic (structural, 20% infil on left) 

RE: Under extrusion?

Underextrusion is only when there are gaps between the lines. It's normal that lines on top surfaces are visible. It's the nature of FFF printing technology. If you want to get rid of them, you can use Ironing function in Slicer. But It may significantly increase print time.

Benchy's are torture tests, don't bother printing one before your first monthly maintenance session - and only then if you suspect there may be some settings adrift.

What would ‘settle down’ after transit?

Anything that has been squashed, shaken or bumped out of optimum in transit.  It is normal for new, complex machinery to take a little while to run-in and to operate more sweetly afterwards.  For a classic description of the process read ' The Ship That Found Herself' by Rudyard Kipling - it's available on line, things have only changed by degree in the 130 years since the short story was written.

My friend still says this is underextruding given the visible lines on the roof.

Your friend is wrong.  Don't meddle with any settings for a couple of months.

Cheerio,