Peak dates, and what they change
A peak date is a day when the city fills up, and the only thing it changes here is that a deposit is asked for whatever else is true of the booking.
Some days in Amsterdam are busier than others in a way that is entirely predictable. King's Day. Pride. The Amsterdam Dance Event. The run between Christmas and the new year. A week when a large conference takes most of the rooms in the city. Those are what this site means by a peak date, and the house will name them plainly if you ask.
What changes
One thing. Half of the figure goes ahead, even on a booking that would otherwise carry nothing, such as a returning guest's same-day hour at a city address. That is the whole of the difference.
What does not change
The figures do not move. There is no premium for the date, no surcharge for the crowd, and nothing added because the trams are full. The arrival window is the same forty to sixty minutes for a central address, and the rules about what a thread settles and what it does not are exactly as they are in February.
Why a deposit on those days
Because the hours are the scarcest thing anybody has on a peak date, and an hour given up at short notice on King's Day cannot realistically be refilled. The half sent in advance is what makes it fair to hold that hour open in the first place. Book early on those dates if a particular name matters to you, and read the deposit and cancellation page before you do.