I suggest looking at the numbers instead of guessing (incorrectly). I’ll save you some time - it’s on page 4. see also page 57 - comparison to other studies finding the same.
https://assets.publishing.service.gov.uk/media/5bfd2209e5274...
It includes students. They clearly benefit the country by spending lots of money but they do not have income of their own (usually funded by parents) so pay little tax - but the subsidise universities by paying high fees, and inject money into the economy from living expenses on top of that. Fees alone can be many tens of thousands of pounds a year for a STEM subject at a good university (IIRC computer science at Oxford is £60k/year). The definition of overseas students also includes many British citizens, even some of those who have been back long enough to pay UK fees.
It excludes visa fees, NHS charge etc.
A lot of the revenue contribution is estimated.
It says non-EEA immigrants make a much larger contribution then UK natives.
The big expense for non-EEA immigrants is educational expenses because they have children. If those children remain in the UK as adults that is an investment and benefits the country in the long term.
That reflects a fundamental flaw, in that it only looks at direct effects for revenue, not the total economic effect. A skilled worker is of far more value to the economy than just their taxes.
On the other hand they do include "public good" as a cost.
It looks very much like a consultancy company telling the client what they wanted to hear. It was commissioned when Theresa May, who was pro-EU and anti-non-EU-immigrant, was Prime Minister.
How much credence do you give it? I'm not an economist, and my general approach to any government's publications (especially in economics) is one of scepticism. Especially if it aligns with the party line (published in 2018, under May, who was very strongly anti-immigration).
Edit: this isn't made by the government but by a university, so scepticism is lessened slightly.
See my other comment for specific criticisms: https://news.ycombinator.com/item?id=46013937