It's a huge red flag and I don't understand why people flock to such risky investments.
@Craig I genuinely hope you make a shit load of money from that coin. But please don't invest anything you're not comfortable with losing.
If they're offering a guaranteed 19.4% ROI they are gambling on a continuous wave of new 'investors'. There may well be a big wave now, but it won't last forever and that coin will sink. There's no safe way of knowing when to time the market in any investment. If you know about 'upgrades' that are going to boost the price, then everyone does and the price will already reflect those upgrades. They'll continue to offer you the 19.4% ROI by creating more coins (leading to hyperinflation and the subsequent devaluation of your actual monetary investment).
Getting 20% more coins from them is pointless if the coins are worth fuck all.
My advice as a concerned bluemooner is to get out whilst you're up and invest in something more tangible!