A:Answer I do not know the specifics in regards to this particular lamp for use in light therapy but I think this information should be helpful.
5000 lux hours/day is recommended (at least for seasonal affective disorder, it may be different for other uses of light therapy). So if you are using 10,000 lux settings you would want to use the lamp for 30 min every morning, ideally before 8AM. and you should sit about 16 in from the lamp.
Check out this article for more details and answers to your questions. you should be able to find it by the link at the bottom.
J Psychiatry Neurosci. 2005 Jan; 30(1): 72.
What is the optimal implementation of bright light therapy for seasonal affective disorder (SAD)?
Robert D. Levitan
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC543845/