It is the maximum number of results/records that will be displayed in the drop down lists/combo boxes or in any other list boxes that reflect the available or linked records or results of a search, inquiry or update.
Make the necessary changes in the text box in the "Value" column. Setting this value to low will result in certain lists not being fully populated.
Setting this value to high may allow the user to over tax the network and server, and in some instances, totally deplete the virtual memory of the client machines with excessively long populations of drop down lists in the system.
This setting can have a value between 200 and 5000.