Please, remember that ADST -> ADS conversion ends on the 30th of June 2019. After this date, it will not be possible to convert ADST into ADS anymore.
The token swap will be done at a 1:1 ratio. This means that one ADST ERC-20 token will be exchanged for one ADS coin. There will be no cost for the swap except the Ethereum Gas cost for the transaction.
Please keep in mind that once the process is over, it will not be possible to convert your ADS coins back to ADST ERC-20 tokens. After the 30th of June 2019, the ADST ERC-20 token will not be usable and will not be supported by Adshares. Please make sure to swap your tokens before the deadline.
Also, keep in mind that, depending on the number of conversions, the later you will start the conversion process, the longer it may take, so we advise to start the procedure before the 20th of June, 2019.