Thank you for the comments.
It was a bug in my patch as another developer says.
I've not considered about the value 'zero', sorry.
I attached new patch.
This patch rounds up the value when only it's less than required unit.
Like below.
(unit: min)
0->0
0s->0
10s->1
70s->1
Although my original complaint is fixed, I'm worried about this change will make users confusing.
Is it better to raise a message(ex. INFO) when a value less than required unit is set?