"Usually" is the word to hold onto in this question. The source gives a wide span, and the span is the honest answer.
What Cleveland Clinic says
Cleveland Clinic writes: "But it can take anywhere from a few weeks to a few months for your plantar fascia to heal."
The span runs from a few weeks to a few months. It is phrased as what "can" happen, so it is a possibility range and not a schedule.
What the sentence leaves out
It does not say what makes one person's healing faster than another's, and it does not say when to worry.
Two studies on treatment are linked here if you want to see how researchers approach it: an open-label randomized trial of focused shock wave therapy for plantar fasciitis and a systematic review of physiotherapy interventions.
What to confirm, and with whom
Ask a foot doctor near Itasca where your heel sits inside that span and what they would expect to see change at the next visit.
The clause readers skip
The sentence opens with "But," which marks the span as a qualification. Treat it as a range to check against your own heel, not a promise.