Unsure of VAT treatment (Reverse Charge or Not?)

Hi,

I have an invoice from a US supplier who have put this on the bottom of their invoice which threw me a little:

"VAT Reverse Charge Notes: No VAT charged. Customer provided VAT registration number and may be responsible for VAT fees"

They provided an "EU" VAT number but have also stated No VAT charged. So I am a bit confused as to the treatment for this? Any clarification would be appreciated. 

The supplier is Alexa Internet if anyone has had dealings with them as well.