Deficit rainfall, reduced sowing: Estimates overstate food grain produce?

Possible because of the way the estimate is calculated

Food grain production is expected to touch a record 141.6 million tonnes in 2018-19 (kharif season) according to the 1st advance estimates of crop production, up from 140.7 million tonnes last year. 

This is despite the fact that rainfall from June to September has been around 10 per cent lower than normal and sowing has declined by nearly 4 per cent compared to last year. 

Why is this so? Have the 1st advance estimates overestimated food grain production this time around? Will actual output end up being lower than what has been estimated? 

It is difficult to say for sure.