Import small csv file to calc results in huge ods file

I have a small csv file of transactions downloaded from my bank. It is 71 lines total size 7K.
When I import into Calc and save as an .ods file, it ends up as 6.3 Meg in size and brings the computer to it’s knees when saving (or trying to do just about anything with it.)… It takes about 3 minutes to open the file
I’m using LO version
When I save it as an xls file, it ends up 2.8 MB in size and opens and closes without delay and I can manipulate it without delay.
What is going on here?

And the import result is fine? With Ctrl+End is the selected cell at bottom-right of data?

Ah Ha!.. very astute of you (and clueless of me).
There were 55 rows of data and then about 30 blank rows. After that, there were 1,104,000 rows where the last two columns of data from the first 55 rows were repeated…
Not sure how that happened but don’t think it was something that I did (even in my cluelessness).
(When saved as an xls format there were only 64,000 extra rows so it was faster.)
Thanks… cleaned up now.