wat is auto split keys

Sets whether a key is automatically created for a new record placed between the current record and the previous record.

Applies To
Forms
Pages

Property Value
Yes if the key is automatically created for the new record; otherwise, No. The default value is No.

Remarks
To set this property to a value of Yes, the following conditions must be met:

The current key must be the primary key.

The last field in the primary field must be an Integer Data Type, BigInteger Data Type, GUID Data Type, or Decimal Data Type field.

http://mibuso.com/forum/viewtopic.php?f=23&t=17182&hilit=10000
http://mibuso.com/forum/viewtopic.php?f=23&t=34013&hilit=10000

Autosplitkeys is a form property that automatically generates key values for primary keys that end with an integer type field. An example is on the sales order subform. This form is linked to the header table by the document type and document number, and the autosplitkey generates the line number automatically. The reason why they selected the number 10000 is because that way you can insert lines between two existing lines. So if you have line 10000 and line 20000, the autosplitkey will automatically generate line number 15000 when you insert a line between those lines.