Pick a category, then up to 3 devices from it. The stated figures are drawn as concentric arcs, printed as numbers, and paired with what each listing says about a fee. Hours and days are drawn as two separate orbits, never one.
How the arcs are drawn
arc sweep = stated figure ÷ full turn
full turn = 30 days on a days orbit, 72 hours on an hours orbit
a figure at or above a full turn is drawn as one complete turn
Pick one device, how long you expect to wear it, and how many hours a day you use it. It reads back what the listing states about paying, what the listing says ends and when, and how many times the device gets charged over that period. Where an input cannot move the number for the listing you chose, it is switched off with the reason printed beside it rather than quietly ignored.
What you supply, and what the listing supplies
From you: the length of ownership, 1 to 3 or more years, and the hours a day you use it, 1 to 8.
From the listing: the runtime figure, in the unit the listing states it in, or nothing at all where the listing states nothing.
From the calendar: 365 days in a year. That is every number in the arithmetic below accounted for.
The arithmetic, printed
period in days = years × 365
charges, days-based figures = ceiling( period in days ÷ stated days )
hours of use = period in days × hours a day, both of which you choose above
charges, hour-based figures = ceiling( hours of use ÷ stated hours )
where a listing states no figure, no count is produced
There are no prices and no subscription amounts anywhere on this site. Rates change, and a stale number is worse than none. What is recorded here is the shape of the arrangement, never the size of it.