What does the huge number on top mean?
It does not represent anything of significance and is probably a bug (see the links below). It is caused due to the use of Sequential API as it omits the input layer and directly takes the embedding layer as input. It can be removed by the use of functional API or by commenting out this in keras/engine/sequential.py :

@property
def layers(self):
    # Historically, `sequential.layers` only returns layers that were added
    # via `add`, and omits the auto-generated `InputLayer`
    # that comes at the bottom of the stack.
    if self._layers and isinstance(self._layers[0], InputLayer):
        return self._layers[1:]
    return self._layers


You can take a look at issues raised on github regarding this here and here.