xth_data table in BPS user exit

Hi,

I am writing a user exit function module and notice the following:

when I get into debug mode, I notice that the data record sequrence is not what I can see from the BPS layout. The first record in the layout become the last record in the xth_data table while the last one become the first.

I have a column where user only need to input the first record and the user exit need to populate this data into all following record.

Any idea how could I make the xth_data table's record to be the same order like the BPS layout?

BTW, I include all the characterisc in the filed to be changed of my user exit, so all the data will pass to the xth_data once.

thanks,