question about specify installation folder

If my default installation folder is:
C:\Program Files\12345\

and if I specify the installation folder to:
C:\temp\

the installation will automatically add again the folder name at last like this:
C:\temp\12345\

is there any way to get rid of it? I know I can manually take out the '12345\' myself, but for most of regular users, they won't notice that. So they will install at the wrong folder.

I realize if the temp folder already has 12345 folder, then it won't add another one again.
is that true?

I realize if the temp folder already has 12345 folder, then it won't add another one again.
is that true?

if you mean add a new 12345 folder under the temp\12345 dir, the answer is no, but if you mean a new 12345 under temp, this is not possible, have you ever tried to create 2 folders into a dir with the same name? :-)

You might want to add a backslash to the end of your InstallDir command (nsis manual chapter 4.8.1.21):

InstallDir "C:\Program Files\12345\"