How 1month, 2 month lag series Work?

Hi All

We are using Demantra 7.3.0.1. Recently we noticed for many items, 1 month lag forecast is not equal to 5 week lag forecast or 6 week lag forecast. We do booking & shipping collection weekly and we also run engine in that frequency. Our forecast buckets all in week format.

How the system calculate the 1 month, 2 month lag forecast? We did average for 4 week lag and 13 week lag forecast and still it doesnt match with 2 month lag forecast!

Any idea? We are using standard series which came through initial installation.

Thanks

Roger