Thanks for the fast response.

I'm guess I'm unsophisticated so I don't know what it means and therefore I cannot be aware of the effect. What does the warning mean?

never mind. I was confused by the word "but". I would have thought it should be "and".

Using TIM_DIV1_CLOCK for shortest and most accurate timer

As the warning says, when you select TIM_DIV1_CLOCK, you have more accurate timer, but the longest possible ISR timer will be shorter (because of the number of bits, 32/64, used to count, uint32_t or uint64_t)

On the extreme side, Using TIM_DIV256_CLOCK for longest timer but least accurate means when you select TIM_DIV256_CLOCK, you have less accurate timer, but the longest possible ISR timer will be longest.

The selection depends on your use-case. First try the best TIM_DIV1_CLOCK, if not long enough, reduce gradually to USING_TIM_DIV16, then the worst USING_TIM_DIV256

Thanks. (I wish there was a like button.)

You're very welcome. Your words are more than enough.