If you see less records in the record tree then in the record grid, this will happen when invoices of another year are booked in the active year.
The screen below show a record with a date of 2013 in the bookkeeping of 2014.
This is not wrong if you think this record has to be booked in that year, but the record tree will not show it.
You can select it and find it with search or in the record grid.