Double followed by bidding a suit is always 5-card
The South hand could bid 1N, but I assume QJ is not enough as a stopper (but practical). So from that point it is OK to double.
So the right bid is 2C showing typical 18-19 and 3-card support, but primarily and with no better bid.
069B5AC88C6EF7A3F5E22F9D4332
Double followed by bidding a suit is always 5-card
The South hand could bid 1N, but I assume QJ is not enough as a stopper (but practical). So from that point it is OK to double. So the right bid is 2C showing typical 18-19 and 3-card support, but primarily and with no better bid.