The only way to know your own gauge with a particular yarn and needle size is knit a gauge swatch. Start with the needle size suggested and if that doesn’t give you gauge then either go up or down a needle size and try again. You only need to make the gauge swatch about 4x4. Enough to measure the stitches in the center of it.
The gauge you listed would be 4.25 st per inch. That extra .25 can make a difference over a large amount of stitches. How important it is depends on the project and what stitch will be used.