The ceiling is in units, not yen
Every service under the insurance carries a number of units. How many units you may use in a month is capped by your care level — that cap is the monthly ceiling.
What a unit is worth in yen depends on the city and on the type of service. You will often see a figure like "362,170 yen for Care Level 5". That is the national calculation at ten yen a unit. In urban areas a unit is worth more than ten yen, so the real ceiling is higher.
You are not meant to use it all
The ceiling is a limit, not a target. You pay 10–30% of what you actually use, not of the ceiling. What to use, and how much, is decided with your care manager or a community support centre.
What happens if you go over
Anything above the ceiling is paid in full by you. The insurance does not cover the excess. A care plan is normally built to stay inside the limit, so talk to your care manager in advance if you need more in a particular month.