If config.month & config.year are equal to config.range.backLimitMonth / ..Year, then some months from before back limit may be displayed at first.

[janzankowski]

This is because the month-year defined by config.month & config.year is set to be displayed as the right-most month at first render of the calendar.

What's also not ideal in such a situation, is that the first click on the "previous" button will actually move the calendar forward, making the left-most month displayed be back limit (= config.month & config.year).