After applying the source estimation method, we get a 301-dimensional array.
What do the values in this array mean? If we plot them, what do their x-axis and y-axis mean?
The source estimation process and the output files are documented in the introduction tutorials:
https://neuroimage.usc.edu/brainstorm/Tutorials/SourceEstimation
If you are interested in using Brainstorm for processing your data, I recommend you start by following all the introduction tutorials (section Get Started), using the example dataset provided:
https://neuroimage.usc.edu/brainstorm/Tutorials
If you observe behaviors that are not explained or different from the tutorials please post a detailed report here: explain the data you have in input, the options you use, the expected output, the results you get instead. Include screen captures for clarity, showing the files in the database explorer and the graphical rendering you have in Brainstorm.