This value represents your current annual NXS rate of return (%).
The rate starts at 0.5%, and can increase to 3.0% after 12 months of consistent staking. The rate increase is non linear, slowing in terms of its increase over time. It takes several weeks of consistent staking to reach 1.0%, and around four months to reach 2.0%. With this rate, you can calculate the average amount of NXS you can expect to receive each day for staking.
It is possible to stake with any amount of NXS at a rate of 0.5%. However, as of the 6th of June 2019 it takes around 10,000 NXS to be able to reach the maximum stake rate of 3.0%.
Similar to other forms of mining, Proof of Stake mining has a level of difficulty. As more people successfully stake on the network, the difficulty of staking increases. This results in an increasing amount of NXS required to increase the stake rate. Furthermore, a larger balance of NXS in your wallet will increase the frequency of NXS rewards.