Invoice Numbers out of sequence

Hi

I am using MYOB Essentials.

On the page which lists all the invoices, the invoices are sorted out of sequence. I have the down arrow on the number column. The last invoice is INV1000 but it does not show at the top, it shows up down the bottom.

It looks like MYOB shuffles the invoice to the bottom because it has clicked over to 1000. Using the 1 to sort instead of using the whole number 1000.

How can I rectify this?

I hope this makes sense!!

Thanks

Rod