Congratulations, you are a data owner now!
This is nicely added on top of your responsibilities. (most likely)
Some suggestions for activities not to do considering your limited time:
1. Do not act like a data definition is a state secret
It can be puzzling to keep a secret sometimes when an idea needs to mature further or to surprise.
However, rules & definitions of data should be like a good news to be spread easily around the organization.
Once the data definition and rules are commonly known and easily accessible, as such it will set the ground for people to follow them.
2. Do not have as much data as possible under your ownership
Data governance is not a game of football, where the team that scores the most goals wins the match.
Having more data terabytes to own will not make you successful; instead, how well definitions under your ownership are guarded and shared.
All owners are equally important, however you can be the roll-model by doing your job well and inspiring other data owners.
3. Do not go for more, go for less
Less different definitions will create more valuable data and more knowledgeable workers.
A definition or business rule should not be as long as a blog, detailing with everything.
Some level of abstraction is healthy to come to a faster agreement on ownership and more concrete rules.
4. Do not have endless technical discussions around which format, table or storage data is stored
As a data owner you are responsible of the data definition and sharing the knowledge around the data.
This is where your responsibility ends.
It is however the responsibility of IT to see how this data will be implemented, of course in line with the rules given.
5. Do not forget the open minded aspect of being a data owner
When dealing with data requests, you should look at the entire organization and not solely the part you know very well.
All these are equally important, despite your favours and areas that are of your interest.
No doubt that by doing something right, will save quite some hours and remove overtime.
So challenge us how to master your data owner skills and putting your attention on the right items.