This is a shady website as well as there service offer. First of all, What is your reason for using this kind of service? There tool is for scamming people and I don't know if double spending is still possible on the current code of Bitcoin.

Stay away on that services. If you want boost your unconfirmed transaction. Its better to use TX accelerator services like viabtc. https://www.viabtc.com/tools/txaccelerator