Learning how to do edits of your own music tracks is a crucial skill to have as a music composer for media.
Most broadcast stations will allow different length for commercials spots, for example: 60 second, 30 second and 15 second.
Some companies will produce and use all three of them for different marketing campaign. For example: a 60 second edit could be used for a national TV ad, a 30 second for a local commercial TV spot and a 15 second for a web ad, like the ones you see on social media.
As a composer of music for media it is important to make these edits of your tracks and have them available in your portfolio for the client. This will help you stand out as a music producer and increase your chances of having your music licensed.