Hola!! It means means Manuel's house has two floors!! = La casa de Manuel es de dos plantas

Hola Christina. La casa de Manuel es de dos plantas/pisos =Manuel's house is on two floors. La casa de Manuel esta en el segundo piso = Manuel's house is at the second floor. La casa de Manuel tiene dos plantas/pisos= Manuel's house has two floors. "de" preposición 1. Indica la persona o cosa que posee el nombre al que complementa. "Indicates the person or thing that has the name that complements." "el libro de Juan; la casa de mi padre; los árboles del jardín; la puerta de la casa; los condimentos de la comida" 2. Indica la persona o cosa que tiene una determinada cualidad. "Indicates the person or thing that has a certain quality." "el color del cielo; la altura del edificio; el volumen de la música"

In the phrase you mention there are two "de". When you say "La casa de Manuel", "De" is used to express possession. Manuel possesses that house. On the other hand, when you say "De dos pisos", you're using the preposition to describe a noun using another noun. "La casa de dos pisos", "El vaso de agua", "El juego de fútbol". In all of them "de" is used to describe nouns.

Hi Christina It means Manuel's house has two floors. In regard to "de" its a preposition, and its use establish a relationship of dependency between two or more words. For Example: - I am from China= Yo soy de China - Manuel's House= La casa de Manuel - My mom's husband= El esposo de mi mamá - Chocolate Ice cream= Helado de chocolate