First of all, the existence of a tag does not indicate being on-topic. Anybody with 300 reputation points can create a tag, and there's no specific review process for that. In fact, if you look around here on Meta you'll see a lot of recent requests to remove or blacklist useless or off-topic tags.
Specifically regarding Android, there are some questions relating to Android that could be on topic. Refer to the FAQ to see specifically what is on topic for this site:
Super User is for computer enthusiasts and power users. If you have a question about …
- computer hardware,
- computer software, or
- personal and home computer networking
and it is not about …
- programming and software development,
- video games or consoles,
- websites or web services like Facebook, Twitter, and WordPress,
- electronic devices, media players, cell phones or smart phones, except insofar as they interface with your computer,
- issues specific to corporate IT support and networks,
- asking for a shopping or product recommendation,
… then you’re in the right place to ask your question!
A question about how Android interfaces with a computer would be allowed; thus the tag is a valid one to have around. Questions more specifically about Android should be asked on the Stack Exchange site for Android Answers.
Deleting your own question will restore the reputation points lost. Beware though that if you ask a lot of questions that get downvoted, closed, and/or deleted, you may be automatically banned from asking any more questions in the future. As such, you should be careful about deleting questions, and instead work to ensure that your questions are on-topic before asking them.