Likes eating more than drinking milk

So I am finding it difficult to feed my 7 month old formula. I am worried he isn’t getting enough milk in the day. My breast milk started decreasing around 5 months so I have been topping up with formulas and around the 5-6 month mark started introducing purées.

My guy will feed from the boob for around 7 mins (doesn’t sound like it’s super strong let down most the time) and then I will top him off with formula and then feed him oatmeal in the morning, purées at lunch and dinner time. Afternoon I’ll give him a snack like fruit or some baby crackers along with the the milk. When I top him off with formula he usually will only drink 30ml at most. I don’t know exactly how much he’s getting but I feel like it’s a lot less than the recommended. Does anyone else have this issue? Would you be concerned?