Physics question help please

Hi, please could I have some help on this question?
https://ibb.co/JFc91YsM
If it says including fourth order, surely n should equal 5 because it’s including 0?
Thanks!

Not sure what is your logic in concluding n should equal to 5.
Let say in maths, we say the maximum value is 10, so you are telling me that 11 is included.
PS. If possible, can you upload the picture to your post? It would reduce the inconvenience of seeing the question.

I meant since there is a zeroth order maximum and it goes up to 4, 0,1,2,3,4 is 5 nunbers?

Yes. If you are interpreting in this way, which I would discourage.

Isn't n the number of maxima and we always have to include zeroth order?

No. (Recall what I mentioned in reply 4)
The symbol n in the diffraction gratings equation (d sinθ = nλ) is the nth order of maximum NOT the number of maxima.
See the image below.

m in the image is the same as the n in the diffraction gratings equation (d sinθ = nλ).
How many maxima are there when m=n=2? There are 5 maxima or bright fringes NOT 2 maxima.

I'm pretty sure you're wrong and I'm right

would need to see the mark scheme to check

So to clarify n is the nth order maximum which would be 4 but the number of maxima would be n*2 +1?

Yes.
Note that I make some amendments in red and italics.

Thanks!

A word of advice if you are taking CAIE A-level Physics:
Be clear about the notation in the physics formula.
Many students are losing marks all the marks of the question because they wrote contradicting "things" when they can be awarded method mark. A few threads of yours reveal that you have a high chance losing such marks.

Do you mean what the symbols mean? Thanks