Why pressing enter is opening first record in child table


When doing sales invoice or order or when working in any child table, if I added an record and I opened the details of that record (by pressing on the last column in the child table), then if I closed it (the details of that record) and I added another new record and I changed the rate and pressed enter, then it is opening the first record details (the record that I opened its details), why? Very noise.

Is it settings problem or bug?