An estimate is a figure for a time that has already passed. In Place Forecast, estimated figures include the jump-off year and anything to the left on charts. They come from data the Australian Bureau of Statistics has collected and calculated. The word "estimated" does not mean a rough guess. It means the ABS has used the best data it has to work out the number. For example, the estimated resident population draws on Census counts, birth and death records, and migration data.
Figures to the right of the jump-off year are projections, not estimates.