Beware as this is going to turn out to be a pyramid Ponzi in the end. The returns are guaranteed because the price of their token keeps rising as more people enter their market. People re-investing also pushes up the price. You send them X Bitconnect tokens today and by the time they pay you back (in USD only) their token has gone up drastically and they are repaying you a fraction of what you actually invested if you consider market prices.

For example someone who invested in them when the token was $1 each might have put in $1000 or 1000 BCC tokens. The loan would now be repaid PLUS all of the interest so maybe $2-3K total after around 4 months (but they lock up the original amount for 299 days) however the tokens you gave them are now worth $65,000. The price will continue to rise until they collapse or are shut down.