Key Settle in refers to the settlement period of the referred Tradable, expressed as an object of type
If it is non-zero, then the referred Tradable is equivalent to a forward contract on the respective spot settling Tradable.
For example, if it equals and the referred Tradable is bought today, then legal and financial ownership is not realized immediatelly, but rather after 2 weekdays.
For most tradables, a small settlement period has no effect on their price, due to the fact their associated cash flows - such as dividends for tradables of type - occur generally at distant future times.
For tradables of type though, the settlement period is important, since a Currency does not pay interest income to its purchaser between transaction date and settlement date.
In the common case where a Currency is used as the reference Tradable in the price calculation of another Tradable, the Currency's settlement period will always have an effect on the calculated price.