The ledger described there is not set up for display in a portal, but in a list view where you can sort your transactions by product, then by transaction date to group records by product and to restart the running total summary field total back to zero with the start of each new group.
Thanks for the advice, i will test it on List view
also, Would it be possible to do it inside the portal or it isnt needed? the main purpose is to precisely track the movement of inventory as possible. I like to see it in the portal because i add/subtract inventory using a Portal.