Numbers inserts a space after a word when i select one of the options offered by my iPad

You can keep predictive text on, just don't use it in Numbers. I'm not seeing how you are getting a space character when not choosing from the predicted text. Can't you just type the entire word/phrase and hit Return?

Numbers builds its list from items that are currently in the column. The thinking is you may want to repeat one of those items. It presents a list of the ones that match what you are typing. It is not doing anything predictive. 2500 rows of data probably presents quite a few matches to choose from. Are all your entries different?

Or you can use the predictive text and always remember to hit backspace (to delete the space) before hitting Return.

Numbers offers those options based on what it sees above or below in that column.

You need to check the column to find the cell or cells where you have that extra space and remove it.

Then, whenever you start typing, Numbers make suggestions that include the extra unwanted space.

On the Mac you can turn off the automatic suggestions by going to Numbers > Settings and unchecking 'Show suggestions when editing table cells'. I'm bot sure if that option is available on the iPad (I don't have my iPad with me to check). In any case, it is a useful feature to have on. Your best bet is to hunt down and remove the extra space somewhere in the column.

SG

I turned on predictive text to see what would happen and it appears you are choosing from the predictive text choices, not from the choices presented by Numbers. If you choose from the choices Numbers gives you up by the cell, you will not get the extra space. You can leave predictive text on, just don't use it. Use the choices Numbers provides that are based on the items already in the column.

Another option is to change the formula so the matching rows with trailing spaces get counted also

=COUNTIF(A,REGEX(A2&" *"))