I suggest you take a look at the ongoing development thread, where lots of YAC stuff is discussed including this one:
https://bitcointalksearch.org/topic/annyac-yacoin-ongoing-development-206577
But long story short, it simply means the original developer added a checkpoint for a 10 day old block. Checkpoints are normally used to force people to update the client but there's little sense in YAC and especially with such a short window, so it's most likely a leftover from early development.
That's why it gives that message. Windmaster already fixed his version to remove the warning, but if you don't wanna update it's safe either, just ignore the warning, it doesn't affect functionality at all.
https://bitcointalksearch.org/topic/annyac-yacoin-ongoing-development-206577
But long story short, it simply means the original developer added a checkpoint for a 10 day old block. Checkpoints are normally used to force people to update the client but there's little sense in YAC and especially with such a short window, so it's most likely a leftover from early development.
That's why it gives that message. Windmaster already fixed his version to remove the warning, but if you don't wanna update it's safe either, just ignore the warning, it doesn't affect functionality at all.
