You are able to edit a meal payment accidentally changed, by going to -
Admin>Meals
From here you would choose either Student Meal Payments or Staff Meal Payments - depending on the payment that needs to be edited.
Once you have chosen a year group for students and clicked choose, find the student in question and click on the figure in their "Paid to Date" Column.
Next, a pop up box will come up listing all the payments that have currently been allocated to this student, click Edit on the payment you need to remove.
Then simply click delete.
For a staff member -
Enter the dates required and follow the guidance above.