This is a known issue.
Based on the code the DaySinceLastFullBackup is a double type which means it has a fractional part as well as whole part (for example 1.25 or 1.5 days). Therefore either value can be used (whole number or fraction)
Configure the days in fractions as well, to allow for the time that the backup takes, and maybe some leeway as well. So, a value of 1.25 days will give you 6 extra hours to the one day interval.
