Screen resolution - very dumbest question

Hello guys :earth_americas:
I have to ask you what is probably going to be the dumbest question in the whole forum, but one that I have problems with … and I can’t find anyone to help me.
I attach the screenshot, where the situation is very clear: my phone’s viewport is 393px x 720px, but if I set the artboard on axure with this size, the design is smaller than the actual viewport size (you see two bands gray above and below the design, screenshot taken from my phone).
Can anyone tell me what should I do please?
And if possible, also explain to me how to correctly calculate the measurements in these cases (I have seen several formulas online, which also provide for the calculation of the dp resolution, but it seems to me a difficult calculation for such a simple thing).
Hoping to hear from you soon,
I wish everyone a good evening :muscle: