Enter an Accession Number (2 letters and 6 digits) and click 'Show list'.

The mutation list will now appear in the upper box

To check the sequence, open the matching GenBank page and select the FASTA display.
Open GenBank

Now use CUT (Ctrl-C) to fetch the whole of the sequence starting at 'GAT'.

Next PASTE (Ctrl-V) the sequence into the lower box and click 'Check the FASTA list'.

The message '** Check OK **' shows the sequence has not changed since the last update.