I've checked on three different browsers, and I'm getting the same very incorrect number for 6 hours. All the other numbers are ranging from 8-12 sats/vbyte at time of writing, but 6 hours says 56 sats/vbyte, which is obviously incorrect.
Further, on looking up a transaction, the "expected time" is always 30 minutes - 6 hours. I looked up the transaction which is currently top of the mempool with a fee of 442 sats/vbyte, and a transaction with a fee of 1 sat/vbyte buried under 68 MB of other transactions. Both said 30 minutes - 6 hours.
It's a nice site, but it needs to be more accurate than this for it to be useful.
Thanks for your response and i see that. the 6 hours and 12 hours is for sat/byte -> legacy transactions not segwit but i didnt bothered to change.
it happens sometime where there is very low fee. also only fastest, 30 min and 1 hour is real-time

I will change the lookup data to be more exact, thanks.