Clarify CListBox::InitStorage parameters

The meaning of the lParam has been a source of confusion. Clarified the text for lParam and cleaned up the wParam, return value, and blurb. (Also avoid overselling the message. Change "the shortest possible time" to just "more efficient". Because it's still not "the shortest possible time", but it's shorter than it would be without the message.)

https://groups.google.com/g/comp.os.ms-windows.programmer.win32/c/MtviqqbHDQs/m/2a2PGs0xmJMJ

This is the MFC counterpart to win32-pr#3259

Author: oldnewthing

docs/mfc/reference/clistbox-class.md

@@ -873,20 +873,20 @@ int InitStorage(
 ### Parameters
 
 *`nItems`*<br/>
-Specifies the number of items to add.
+Specifies the number of items to for which to reserve space.
 
 *`nBytes`*<br/>
-Specifies the amount of memory, in bytes, to allocate for item strings.
+Specifies the amount of additional memory, in bytes, to allocate for item strings.
 
 ### Return Value
 
 If successful, the maximum number of items that the list box can store before a memory reallocation is needed, otherwise `LB_ERRSPACE`, meaning not enough memory is available.
 
 ### Remarks
 
-Call this function before adding a large number of items to a `CListBox`.
+You can call this function before adding a large number of items to a `CListBox`.
 
-This function helps speed up the initialization of list boxes that have a large number of items (more than 100). It preallocates the specified amount of memory so that subsequent [`AddString`](#addstring), [`InsertString`](#insertstring), and [`Dir`](#dir) functions take the shortest possible time. You can use estimates for the parameters. If you overestimate, some extra memory is allocated; if you underestimate, the normal allocation is used for items that exceed the preallocated amount.
+This function helps speed up the initialization of list boxes that have a large number of items (more than 100). It preallocates the specified amount of memory so that subsequent [`AddString`](#addstring), [`InsertString`](#insertstring), and [`Dir`](#dir) functions are more efficient. You can use estimates for the parameters. If you overestimate, the extra rmemory remains allocated; if you underestimate, the list box will allocate additional memory as necessary.
 
 Windows 95/98 only: The *`nItems`* parameter is limited to 16-bit values. This means list boxes cannot contain more than 32,767 items. Although the number of items is restricted, the total size of the items in a list box is limited only by available memory.