What Does Triple Layered Endometrium Mean?

Dear sir, My age is 44 years. Since last more than 1 month, I have been having my periods – the flow is constant; earlier 15 days it was heavy, but now its reduced. I have had irregular periods since last 8 months or so. The sonography report is normal; however, the endometrium layer is described as “triple layered” and is not given in measurements of units – say “mm”. can you explain what does this “triple layer” mean? Is it normal or some problem? thanks