The 100% fill rate is a technical set up, where we are able to tell your ad server (well in advance) which specific 10,000,000 imps inventory needs to be sent to Criteo. This way only those 10M imps come to us & we buy & serve an ad for all of it. And importantly we pay $1 flat CPM for it. The higher CPM the lower the volume (and hence revenue), however with a low CPM the revenue again becomes low (high volume*low CPM). Hence we recommend a middle ground where the revenue can be maximized. Since Criteo margins are fixed (constant), for us the Revenue is most important. The more we can spend in dollars terms, the more we also make. This is the best transparent business model you will see in the Industry.