Apologies if this is a rookie error.
However looking through campaign data for the exact same date range, my amount of conversions (a web form submission) in the reporting tab is completely different compared to when I look at the attribution analysis tab.
Now my Google Analytics suggests 150 is a more accurate figure as opposed to 284.
My question is why is there such a discrepancy? Or am I just filtering the data incorrectly in the report / campaigns tab - and if so how can I change it?
Adwords measures conversions differently than Google Analytics. Adwords will give credit to the last click in your Adwords account. That's assuming you didn't change the default setting when setting up the conversion tag.
Google Analytics will give it to the last non-direct click. So typically you will see Analytics showing a lower number.
You can get a better idea by looking at the Multi-Channel Funnel > Assisted Conversions report inside Analytics.
Then, add the last click and the assisted. That should narrow the gap.