A lot of the time the advertising posts will be within minutes of looking at something. I will give you an example.
I am setting up an online coaching program and was viewing multiple online softwares that can host the things I need. 2 specifically made the cut. 5 minutes later one of those was advertised to me on ig. Note, I was searching on mullvad, and have never logged into an account on it. I was therefore not logged into anything within the browser. This was on my MacBook
I open my phone, open it on an account not linked to said business, and one of the 2 softwares was in my feed within only a couple of scrolls.
Never been shown to me prior, never ever searched for on the ig account