ATtiny13A Max O/P time? Answered

If you don't mind the processor being busy while the delay is running, you can use nested loops, each decrementing a counter on each pass. For an 8-bit core, setting two of the counters to 255 will get a visible delay, and the third can be used to extend the delay to about 5 seconds. If you are programming in C, there should be a delay function available if you don't want to write the delay yourself.

For a more elegant solution, you should look into whether that microcontroller has any timers, as these will allow you to run other code during the delay, and won't use up as many registers.