What the typical price is
It's the price the product held the longest over the last 14 days, according to our own tracking. When a card shows a struck-through price, it's the typical price, never the "was" price the store wrote.
An example
A pair of earbuds cost $20 for 12 days, went up to $30 for 2 days and is $15.80 today. The typical price is $20, because that's what held for most of the period. The real drop is 21%. If the store advertises "was $30, now $15.80, 47% OFF", DipScout still says 21%.
Why not the average
An average gets dragged by any spike: two hours at an absurd price would already inflate the "before" and manufacture a discount. The typical price is a time-weighted median: each price weighs by the hours it held, not by how many times we read it. A price that lasted less than half the period never becomes the typical one.
Why not the store's "was" price
The "was" price is written by the store itself, and nobody checks it. Often the product was never sold at that price. A number like that looks precise and misleads more than showing no number at all.
When there's no typical price yet
We need at least 3 days of tracking to call a price typical. Before that, the product page shows only the price and the chart we already have. We also don't call a difference smaller than 5% a drop.
And "lowest price in N days"?
It's another measure from the same history: how many days it has been since the product was at or below today's price. If today's price never showed up before, N is the whole time we've tracked the product, and nothing beyond it.
The pre-sale trick
Sometimes a store raises the price for a week or two and, on sale day, goes back to what it charged before. If the increase lasted long enough, it becomes the typical price and the return looks like a drop. That's why we also check whether the product already had today's price shortly before the increase: if it did, it's not a deal, and the page warns you with the dates. More in How it works.