Expression table behavior

I'm new to NX and want to ask about some odd behavior I've noticed with the expression table.  I was entering a series of variables in the expression table when I accidently hit enter twice.  That put a blank line in the expression table between two entries. So I right-clicked on the blank line and deleted it. When I did that, everything rearranged.  The entry below moved to row 2, the entries above shifted down, and row 1 became active (ready for the next input) as shown below.   Before this happened new entries were being added at the bottom of the list.

So is this normal? Why did NX rearrange everything and shift entry to the top? Just trying to understand how this is suppose to work.

Also, is there a way to rearrange the rows in the table if I want the expressions listed in a different order?

Thanks.