The AWR units are the resources which come with every kind of available subscription. Every plan has a number of keyword units, calculated considering the volume of ranking updates. 

1 keyword unit = 1 keyword updated weekly, on 1 search engine unit, with a search depth of 5 pages (default update preferences)

1 search engine unit = first 3 different engines added to project (e.g. Google + Yahoo + Bing).
Any 2 different versions of the same core engine (Google Desktop + Google Mobile) are counted as separate SE units.

Units are computed using the following factors:

Details about the account units consumption can be accessed in the Resources section. 

When using the project scheduler, the application automatically reserves the keyword units required for a month's time updates (for weekly, 4 updates will take place). The same way goes for all available frequencies. 

On the other hand, when running a manual on-demand update (either 1h / 12h / 48h), the application consumes the resources for that one time update. The consumed units are reimbursed when the subscription is renewed / the billing cycle is refreshed. 

For yearly plans, the billing cycle is refreshed on the day of the month when the invoice was issued, so this is the date when the units spent for on-demand updates are refreshed. 

Do you have any other questions? Don’t hesitate to get in touch and we will keep building the FAQ.