The membership option enables you to enter up to 10 images per monthly competition for the next 12 consecutive competitions of Life Framer – so 120 images in total.
At whatever time you become a member, you will be able to enter the current competition and 11 further consecutive competitions. Given that Life Framer runs in editions of 12 monthly competitions followed by a series of exhibitions, if you join as a member during the middle of one edition, your membership will continue into the next edition (e.g. if there are 5 monthly competitions remaining at the point you become a member, you will be able to enter those, along with the first 7 monthly competitions of the subsequent edition).
You are not obligated to submit 10 images to every competition – you can submit less than 10, or skip monthly competitions entirely. However unused entry credits will not roll over beyond the 12 monthly competitions.