Smithy CNC Mills - Manual (Page 65)

On some machines, the carousel will move when a T word is programmed, at
the same time machining is occurring. On such machines, programming the T
word several lines before a tool change will save time. A common programming
practice for such machines is to put the T word for the next tool to be used on
the line after a tool change. This maximizes the time available for the
carousel to move.
SmithyCNC Programmer’s Reference Manual: Other Codes 5-3