Jump lists is one of the most useful features Microsoft introduced with Windows 7 – very late, since freeware applications with similar functionality exist for years. In the Start Menu large icons or in the Taskbar, jump lists contain by default 10 most recent items.
You can increase this number to 20 (or anything, with 60 being the limit), just by right clicking on the Start Menu Flag/Globe, to open the properties of the Start Menu. Then press the “Customize” button, and, at the bottom of the dialogue that appears, change the value of the “Number of Recent Items to Display in Jump Lists” to a number that meets your needs.
The registry key that controls this property is the Start_JumpListItems at HCU\Software\Microsoft\Windows\CurrentVersion\Explorer\AdvancedRelated (automatically selected)