Confound effects beta-maps

Dear CONN experts,

I have 3 sessions of block-designed task with two task conditions. I performed denoising step with the following confounds: WM, CSF, movement, scrubbing, effect of condition 1 and efect of condition 2.

Now, I need to calculate percent of variance explained by effects of each task condition (for all subjects). In setup options I selected 'Create confound effects beta-maps' and as a result I got 'BETA_denoising_Subject*.nii' files (1 file for each subject) and '_list_BETA_denoising.mat' file. How to interpret created BETA files?

Any tips how to calculate % of variance explained by task effects?

Best,
Karolina