Summing days to a date field

Summing days to a date field

Hi, how I want to send a email if the present day is due 10 days from the "Data_de_Registo" when the form was inserted,

the problem is I can´t define the 10 days here, as it gives me the next error.

The Left expression is of type TIMESTAMP and the right expression is of type BIGINT and the operator + is not valid here 

if( Estado == "Avaliação")
{
    if( zoho.currentdate >= (Data_de_Registo + 10:00:00)) . How can I develop this?
    {

sendmail
[
    from:zoho.adminuserid
    to:"xxxxxxx@xxx.pt"
    subject:"iLogic - Avaliação em Falta"
    message:"Bom dia, \nVimos por este meio lembrar que existe uma ideia ainda por avaliar, Obrigado"
    content type:HTML
]
    }
}