By default, iOS’s scale factor of 3.0 (@3x) assets is 1.5 larger than @2X. For example, if your layout size is 750x1334, its @3X will be scaled to a width of 1125. However, we know that the resolution of iPhone XS Max is 1242×2688.
And in some cases, you want @3X to be sized at 1242. There are three ways to do that:
Select any layer and enable “Set iOS @3x width to 1242”:
Select your assets on the right panel and enable “Set iOS @3x width to 1242”:
Download all assets by clicking “Download all assets” in the upper right corner and enable “Set iOS @3x width to 1242” in the pop-up panel：