Recommended oil can actually vary due to climate etc so multiple types can be right and there is overlap.
The first number IIRC refers to the cold viscosity and the latter relates to the hot viscosity (I am rusty so worth checking that).
A lower first number has the potential to circulate around the engine quicker and thus start working quicker and most modern cars have quite low first numbers. Using too high can actually be bad as it is too thick when the engine is cold so modern cars with high tolerances and delicate bits can have problems.
In contrast older (classic) cars that leak and with lower tolerances can have a problem with modern low first number oils and have quite high first numbers.
Down at the 0-30 and 5-30 level there is not a lot of difference in the viscosity aspect and the most important thing to make sure is that it is an approved oil for your car – ie it meets the correct manufacturer specs. These will be listed in the handbook and on the oil.