Hi ,
If you configured it like you stated , it will advertise 1.0.0.0/8 , because eigrp does by default autosummarization.
If you disable the auto summarization , it will advertise with the interface netmask.
For example if you have some vlans with ips in the 1.1.1/24 range , and you are configuring under router eigrp network 1.1.1.0 0.0.0.255, eigrp will adverise all the prefixes matching the network interface , and also send hellos on those interface - if there is no passive-interface configured
Dan