optimal size of innodb buffer pool
If you expect your InnoDB data to grow, you should prepare for it by having a larger InnoDB Buffer Pool.

Where does the idea of having additional 10% extra space for the Buffer Pool come from ???

Please note the following diagram of the InnoDB Architecture



Look in the upper left hand corner where you see the buffer pool. There is a section of it called the "Insert Buffer Part". The purpose of the Insert Buffer is to populate changes to non-unique indexes into the Insert Buffer inside the system tablespace file (a.k.a. ibdata1).

From the diagram, up to 50% of the Buffer Pool can be used to manage the Insert Buffer. That being the case, it would be in your best interests to assign a lot more memory to the Buffer Pool. With a data set of 60M, 256M would be a great place to start,