Say, you have 133 rows in your excel file. The 1st row is the headers (id, name, etc). So this means you have 132 cases that you are wanting to attach assistance to. When you get an error upon upload, you can go to that import and click "Show Import Summary". Yours might say "19 assistance records uploaded". So this means that when the import script reached the 20th case (which is on line 21 of the excel file) it failed for some reason. Look at the row and see if all the information has been provided for that case.  Make any corrections needed.  Sometimes you might find it failed because the case did not exist. If so, simply remove the line of the excel file with the invalid case number and try again. It may then go through or there may be another one that is invalid. Also, in order to prevent duplication of assistance records, each time there is an error, click the "Undo" button on the offline upload that failed, then re-upload with the corrected excel file.