What is the accuracy of the watchdog timer in the Attiny4313?

Question

Atmel AVR

The program on the Attiny4313 goes to sleep, wakes up periodically on a watchdog timer. There is no external clock. Therefore, time is measured only by watchdog. Wathdog is set to 4 seconds, 15 to 4 will be a minute, etc. During awakenings, the delay is minimal - the counter is incremented and, if it is not time to start working yet, it falls asleep again.
As a result, during the 11 hours of programming, 12 hours of actual time passed and the controller was late for an hour with access to communication =)
The timer error is almost 10%?! Is not it too much?
There is no information on this in the datasheet.
Power is about 4V, temperature is about 28 degrees.

Answer 1

1% accuracy for the internal clock is already a "precision oscillator". for a 128kHz watchdog, 10% is normal, given that the voltage was higher than the table. counting time in this way is one of the simple hacks, nothing more.
to improve the situation, you can use a timer with clock quartz, usually in ABR it is t1.