No conversion required
When we rebranded from Havven to Synthetix, it was just a token symbol name change, so there's no token conversion required. However, your wallet may not have updated the name, because not every cryptocurrency wallet enables all ERC-20 tokens to be viewable by default. You can add the SNX token details from https://etherscan.io/address/0xc011a73ee8576fb46f5e1c5751ca3b9fe0af2a6f.
I have less than 50 HAV
When we made the name change, HAV holders with a balance of less than 50 were not issued a Transfer event. This means that for some HAV/SNX holders, Etherscan might tell them they have HAV instead of SNX. For people in this situation, they can manually do a 0 SNX transfer, which should emit a transfer event, which will mean that Etherscan will now recognise their SNX tokens or better just use mintr.synthetix.io to see your SNX balance, stake or transfer them.
Do I have double the tokens half HAV and half SNX?
No. If your wallet says you have both HAV and SNX, you do not have double the tokens that you previously did the HAV balance is dead and replaced with the SNX. If you do not see the SNX check etherscan on the ERC20 tokens tab to see if you have already transferred them somewhere before contacting support. https://etherscan.io/tx/0x9d4b4e2fd9fb9b7ace6a10b085d538d97e689c60613bd08bd62d36dcd44daa8f
If you see only HAV in your wallet on etherscan these tokens are dead and abandoned. You already have your SNX in your wallet but if your balance was less than 50 tokens you cannot see them. Use mintr.synthetix.io to see and transfer them.