Plus-size shoppers have been let down by clothing stores often enough that they read a product page looking for the reasons not to trust it. A size chart that stops at 18, a model whose size is not stated, a photo of a size 24 dress on a size 12 body, or a range that says up to 4X while every colour above 2X is sold out: any of these ends the visit.
We write growth plans for plus-size and extended-size clothing brands that already sell online. The plan covers a Merchant Center feed that uses size_type and real size values so your products show for plus-size searches, product pages that carry hip, bust and waist measurements per size alongside the model's own size, and ad copy that describes the clothes rather than the customer, which is what Meta's personal attributes policy requires anyway.
It also covers bracketing, where a customer orders two sizes and returns one, because that behaviour is a symptom of a fit question your page did not answer.
First, whether their size is actually stocked. Not whether the brand claims to go up to a size 30, but whether this dress, in this colour, is in stock in a 26 right now. Stores that show the full size run with out-of-stock sizes visible, and a restock alert on each, keep the shopper on the page; stores that hide unavailable sizes make the range look smaller than it is.
Second, how the garment is graded. A size 24 is not a size 12 scaled up, and shoppers know the difference between a brand that pattern-grades for a fuller bust, hip and upper arm and one that just adds inches. They look for measurement charts in inches or centimetres per size, not just a number, and they look for the model's height and size worn. If the size 22 is photographed on a size 22 body, that page converts; if it is not, the shopper assumes the worst.
Third, reviews that mention the reviewer's usual size, height and where the garment was tight or loose.
Fourth, the returns policy. Bracket ordering is common because the customer cannot risk a garment that does not fit and has no local store to try it on. A free or cheap exchange makes the first order possible; a restocking fee kills it. The customer who finds a brand whose 20 fits them properly tends to stay for years, which is why fit is also the repeat purchase strategy.