It’s not the total value of assets held abroad that counts, it’s the total value in each category, for example “cash”. So if you have cash in one or more bank accounts outside Spain with a combined total of €50,000, then you have to declare all those bank accounts. However, if the combined total came to €49,000, you wouldn’t have to declare any of them or your cash holdings abroad. Likewise with property – another category. If you own real estate outside of Spain worth more than €50,000 then you have to declare all your real estate holdings abroad. And so on for each category – you only have to declare the assets in each category if they are worth €50,000 or more.
If a Spanish resident has assets outside of Spain, but they don’t add up to €50,000 in any category, then no need to file a worldwide asset declaration (Modelos 720) in Spain. If you combined assets are worth less than €50,000 then it follows there is no need to declare. I hope that helps.