The Spanish authorities are asking people to let their families know they're okay via social media rather than phone to ensure that phone lines don't collapse. So many tourists there I suppose.
To be expected in the early stages of reporting such an incident, I think -
"There has been some confusion, as is typical in these situations, about the number of fatalities. Local media outlets are reporting that 13 have died, citing police sources. Other media, including El Pais, are saying there were at least 10 deaths." (Guardian)