Hi, it is very rarely exactly 25% - usually less though can also be more. It is often less because those voting before 15 minutes lose some of their curation rewards. It can also fluctuate depending on the price of SBD, whether higher or lower than the encoded $1.

Third party sites may also differ from Steemit depending on whether they are using the blockchain price of STEEM or market prices.

mmm... had a deeper look for you and looks like Steemit now publishes post-rewards as actually the post-payouts, hence deducting at source the lost curation rewards. I find that annoying! But it explains the discrepancies. So $2.29 was your post-rewards, with $0.05 lost curation rewards. Note that the author-rewards of $1.718 are also 75% of $2.29.