In each language mode, the expression is evaluated for each stock or commodity currently displayed. When your indicator expression is evaluated, the program steps through the recent history. On a chart or individual data file(s), it proceeds one step per day. On a scan, this is done as one step per market.
The expression "getNumDays" is used to acquire data for analysis. It takes no arguments and returns the number of bars available for that stock or other series. For most, the value agrees with the option specifying how far back you want your scanning file to go. For new issues, this value might be as little as 1. If you wish to exclude such new issues, then please make that option selection through the software.
The remaining listed functions take an integer argument between 0 and (getNumDays()-1). This number tells the computer which day you want. For example, getClose(0) returns the current day's close for that stock. The expression getClose(getNumDays()-1) returns the earliest close available.