First issue: If you're typing all of "Master Card" auto fill is a feature you are not using. Turn it off.
'Also' issues: Numbers is slow with large (and even moderately large) tables. It is further slowed by including multiple header and footer rows.
That is likely (at least partially) due to tables being recalculated whenever there's a change to a table—a behaviour that cannot be turned off.
I don't see an easy solution, although you might find the situation alleviated by splitting your table into six month or quarterly tables.
Let Apple know you'd like this behaviour changed to speed the application; Provide Numbers Feedback using the menu item of that name in the Numbers menu in Numbers.