Estimated difficulty is what the pool calculator expect the difficulty to rise on next change.

For the time being your still mining with a diff of 2.5.


The estimated diff is based on a few factors the key is the hashrate in the network, some coins also implement a logic from preventing the diff to go through the roof or fall through the floor. However there are not too many of these.


What you will often see on alt-coins is that the diff fluctuates by incredibly huge numbers, this because the diff vs profit is very vulnerable while a coin is still young, while the diff is low the profit margin is very high but when the diff is high its a loss over another coin, so people ride the waves mining the most profitable coin at the moment.