A property of a screen related to loops. In other words, a sub-form relates to a loop's item which is to be iterated during data-entry. If you enable the sub-form property on a screen, Askia will display all the loop's items on that screen during data collection.
If the screen has been built up as a question table, be it vertical or horizontal, a sub-form relates to the columns or rows of this question table.
By using the max nr of sub-forms property, you can define the number of lines or columns (horizontal or vertical), your question table will display at once per screen. In other words, you can specify how many of the loop's items will appear on a single screen.
For example:
Suppose we have a screen built as a vertical question table, and this screen's sub-variable's loop contains 50 items, thus equivalent to 50 lines.
We do not want the Interviewer or respondent to have to use the scroll bar to answer this vertical question table. Thus, in max nr of sub-forms we specify the value 10.