Users of the OLAP Services Intelligent Cubes feature in a Strategy 9.x clustered environment may observe that after a period of time from the initial publishing of the cube and executing reports based off it, the size of the cubes as reported by the Intelligent Cube monitor in some cases is different in one node than the other node(s). An example of this behavior for a relatively small cube is shown below.

This is working as expected. The difference in Intelligent Cube sizes is due to the fact that the size seen in the Intelligent Cube Monitor is the Intelligent Cube size + Indexes. For example, in a 2 node cluster, when a cube report is created and executed on one node, the number of indexes on that node increase and the size of Intelligent Cube in the Intelligent Cube Monitor will increase as well. However, if the Intelligent Cube Monitor on the other node is checked, the size of the same Intelligent Cube will be smaller.
For more information on Intelligent Cube sizes, refer to the following Strategy Knowledge Base technical note:
KB33449: Intelligent Cube size increases over time in the MicroStrategy Intelligence Server 9.4.x - 10.x