Owl is a tricky one as there are no hard and fast rules. The principle seems to be 'try this for a while, see if it stalls you, if not, try something else'.
Owl is about expanding your range of food choices while still being in the weight loss phase - albeit perhaps a slower phase than induction. Doing owl by the book means being prepared for stalls.
There are two components of owl. First is introducing new foods - nuts and berries are the first of these, then some different vegetables, then a few more fruits. The idea is you introduce them in order, adding just one new thing per week, or over a longer period if you prefer.
Many people keep their carbs at 20g or not much higher, but introduce nuts and berries. This is what I do. I get 19 daily carbs from the food I eat (11g from my meds) so I try and stay under 30g carbs per day - but I let myself eat very limited amounts of nuts (never more than 5g carbs from nuts in one day and I don't eat nuts daily). Very occasionally I will also have berries. I've done this from the start and have not added anything else in. When I get to about 10st I'll start adding some new veg.
The other component of owl is finding the highest amount of carbs you can eat while still losing weight. Some people stop losing if they go above. 25g. Some people can eat more like 40g carbs daily and still lose, albeit slower.
Finding your carb tolerance level is trial and error and exactly the same as checking your food tolerances. You increase carbs by 5g - so from 20g a day to 25g a day and keep it like that for a week or two. If you're still losing well, increase by 5g to 30g a day.
When you stall for a couple of weeks, you've hit your tolerance level and should reduce your carbs by 5 or 10g depending how much leeway you want.
Personally I keep my carbs where they are as it's fine for me right now and I don't want the frustration of trial and error experiments.
So eventually by doing owl you increase what foods you can eat and how many carbs - though you must always stick to getting 15g of carbs from veg. And you find out what level of carbs will work for maintenance. You just may need to put up with a few stalls along the way.
