It depends on what regime you are using and how much oestrogen etc. The more oestrogen you take (and especially compared to progesterone) and the further you are from reaching menopause - then it is likely the bleed will be heavier. As you get post-menopausal and if the oestrogen dose is low/medium, and there is nothing wrong with your uterus ( eg no fibroids or polyps etc then it is likely the bleed will be small if you are on a normal length cycle.
When I took HRT on a 4 week cycle in very late peri through to post-meno I started having lightish bleeds and eventually these dried up completely so I didn't bleed at all. Ar the time I used 50 mcg oestrogen patch and 400 mg Cyclogest progesterone pessaries (which aren't used much now). I have a bleed now because I have been able to lengthen my cycle as I am well post-meno - and have kept approx to the medium oestrogen dose.
As Taz says also it takes a while to settle and depends how long you have been on the conti regime after being period free too.
Hurdity x