The first 500 blocks was instamined for less than 10 minutes"blocks" : 0,
"proof-of-work" : 0.00024414,
"blocks" : 60,
"proof-of-work" : 0.00024414,
"blocks" : 163,
"proof-of-work" : 0.00097655,
"blocks" : 289,
"proof-of-work" : 0.01562500,
"blocks" : 386,
"proof-of-work" : 0.05882353,
"blocks" : 500,
"proof-of-work" : 0.25646695,
and still no source