Configuration 

In the account settings activate the Analytic options 

Create new Analytic Plans

In the account app go to configuration and select Analic Plans, create a new one or select an existing one to edit it. 

In domain select for which document the analytic sum should be exactly 100% and  in applicability select mandatory 

Create new Analytic Distribution [Not a mandatory step but it will make analytic easier to use]

In the account app go to configuration and Analytic distribution, create a new one or select an existing one to edit it. 

The values you select in the Account prefixe, Partner, Product and Company fields are instructing Odoo that when said values are found a certain analytic structure should be applied.

* you can use one or the four fields (you can set a distribution for when a product bought and when a product is bought by a sold by partner)

* Odoo is flexible, you will be able to adapt the distribution when its applied 

Flow

Create a record matching the selected in domain. If you go over or under 100% you will get the following note. 

While adding the analytic account the percentage in the analytic plan column will be red unless the sum is exactly 100%

When the analytic distribution is allied you should get the following result 

When the analytic distribution is applied you should get the following result