I decided to have Ubuntu to dualboot with Win7.
I have read couple of guides, and it seems that I still can't get this right.

ATM I have my laptop running the Ubuntu CD, I picked in installation type - "Something Else"

and I have 3 Partitions (on the same HD):

1. The 100MB for windows


2. 60GB of Windows


3. 458GB of Data

I want to resize the Data partition to 424GB,
so I will have 24GB for Ubuntu(20GB) + Swap(4GB).

I pick the 458GB partition and click change, and is says
"New partition size in megabytes textbox"

Now what am I supposed to do so it'll be 20GB for Ubuntu and 4GB Swap?

This

1) One time write "20000" and then change again and write "4000"

or

2) Write "424000" to have unallocated space of 24GB?

Thanks in advance!