Well, the fact that it says "19 days" is caused because it calculates the months too. If you add the amount of months in, you'll see "1 month and 19 days", which is (almost?) correct.
To solve your problem, you can use the
total amount of days remaining, by using the "%td" and "%tdw" units. They can also be found in the insert menu button. In the next version, I'm going to extend that functionality a bit more, in case you want to display years and days but no months for example. As for now, the "%td" unit will do just fine.
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