Putting “In” at the beginning of a parameter name has no mechanical function, it’s just to communicate to the person reading the API that the parameter is undoubtedly an input parameter as opposed to an output parameter. In other words, they are trying to reassure you that the caller will gain no new information from this referenced variable once the call to the function completes. This is mostly used in an API that contains mixed “out” variables along with the regular “in” kind.
In terms of code standards though, you’ll find a lot of standards heavily discourage ever using “out” variables because they are confusing and sometimes even impact performance negatively. Generally parameters should just be the “in” kind, and if you do this the need to ever use “in” at the beginning of a parameter name becomes completely pointless since it is implied that all of your API uses “in” params.