Seller is lying at the description: no boost function, only buck: Applying >4 Volt will result in 3.3V, applying <3V: no output. DO NOT BUY IF YOU NEED 3.3V from an input voltage lower than 4V.
Seller is wrong with the description: no boost function, only buck: Applying >6 Volt will result in 5V, applying <5V: no output. DO NOT BUY IF YOU NEED 5V from an input voltage lower than 6V.