It is both 7000 AND 15 Billion or so.
This is possible due to relativity and time dilation.
Or common core math estimating. Just round up to whatever number you need.
When people speak of the age of the universe they very rarely finish their sentences.
The universe is about 15 billion years old from our space/time coordinates and it is also about an equivalent 6 days old from the inception space/time coordinates.
This is due to the big bang and inflationary theory (relativity).