This very well might be a thing in which we are the only people irked by, but allow us to explain. This is a new-ish sign along the G train route at 4th Avenue and 9th Street. Up until this sign was put up, people had to simply know that the G train is much shorter than the platform and that they needed to wait for the train in the middle of the platform, or run towards the train once it arrives. This sign is meant to help those who are not in the know, which is a great thing.
The thing that irks us about the sign though is this: it has the platform in the wrong location and the incorrect type of subway car is shown as a G train. This is the proper G train, which also shows where the platform is in association of the train: