It means that they have time to pre-generate the next seeds you will use. Giving them a chance to give you sets of client/server seed combos that would ultimately lead to your bust. Most gamblers stick to a system or pattern when they roll, and given that the server and client seeds are changed for you, every roll, by THEIR systems, leaves anyone gambling on the site open to roll manipulation all while hiding under the disguise of a provably fair system.
We provide the hash of the next server seed we will use before receiving the player seed, therefore we cannot compute seeds after having knowledge of the client seed
The only way this sort of "provably fair system" would in fact be fair at all is if the user takes his time to re-enter a client seed of his own choice (Not the rigged one the server could give you) after EVERY roll. And let's be honest here, Most gamblers aren't even going to bother checking the seeds..
The server doesn't give you a "rigged" client seed, or any client seed at all. The client seed is generated using javascript by the client.
When I brought this up their moderators were extremely defensive and I believe one of their moderators/admins basically threatened to mute me for claiming the site was a scam without evidence.. Between the signature campaign payouts being botched recently and now the provable fair system being found to be exploitable by the developer, I would have a serious look at the site before you consider using it.
I was very transparent and completely explained how our system works, and the only potential flaws that exist, nobody threatened you, nor did anyone mute you.