First I always have to say that there is not any scientific proof that steaming can reduce clots and fibroids. However, there have been case studies where a steam user observes measurable reduction in the size and discomfort of both clots and fibroids.
If your steam plan was prescribed by one of my trained practitioners, their recommendation of steaming for only 10 minutes is likely connected to a steam sensitivity that they assessed during your intake process. There are medical sensitivities, heat sensitivities and uterine bleeding sensitivities. When someone has a sensitivity, steaming for 10 minutes is very effective and helps to reduce any incidence of side effects.
If you have any questions about your sensitivity or steam plan, please direct those to your practitioner. For a second opinion, feel free to consult with another practitioner at the Vaginal Steam Directory. For fibroids cases you want to select a Peristeam Hydrotherapist or filter for “fibroids” under the skills section. Any practitioner that comes up has taken my module on fibroids (which is a higher level course only available to certified practitioners).