ssas tabluar memory issue

Hi, i have sql server 2016 standard SSAS tabular mode. windows server 2016 i am newbie in SSAS. i have a project to deliver but have huge memory issues. created a new cube. i processed the cube once he was at 1.5GB, after a day i processed again, the memory during process went slowly up to 7 GB after process finished it went back to 6GB ram. what i don't understand is, why doesn't it go back to 1.5 gb as it was before process started, the process just updated the data and didn't add anything! what am i missing? really appreciate any leads! thanks