From the comments, on the Greek primary surplus

Tom Warner writes:

…the budget balance fell off a cliff in December. State budget revenues were only 2.4% below adjustment program target in Jan-Nov, but were 14% below target in December and 20% below target in January. That’s a huge shortfall – if a 20% revenue shortfall were to persist for the whole of 2015, that would be more than €11b euros of missing revenues and more than 6% of GDP.

So the issue now isn’t whether Greece can hit some pie-in-the-sky target, it’s whether it can get back to where it was in Jan-Nov of last year. Syriza’s going to have to get the state finances in order very quickly or they’re going to go boom.

Here is Tom Warner’s blog.