Gradually increase/decrease an arduino sensor reading coming into Unity

Hi I am bringing an Arduino sensor reading into Unity.
I can pass the data from Arduino into Unity without any problem.

The sensor readings are coming from a flex sensor linked to a bicep muscle.
I want to use these sensor readings to generate a HUD Powerbar within a FPS game inside the Unity game engine.(the more the player flexes their bicep the more the energy bar will increase//if the player doesn't flex their muscle the energy bar will decrease).

I've already managed to take the sensor reading and apply it to the rotation of a 3d bottle - it works but it animates very 'jumpy' as the readings don't increase/decrease gradually. What I would like to do is increase & decrease the sensor data readings gradually. ie. if the flex sensor reading jumps from 0 to 80 I would like the energy bar to increase in height gradually in increments of 1 from 0-80 rather than suddenly becoming 80.

I have remapped the incoming sensor readings to be between 0-100 so that they can be used as a % of the height of an energy bar graphic. I've attached screen shots of the arduino sketch as well as the Unity code I used to rotate a 3d object based on the arduino flex data.

Any advice on how to go about coding this gradual change either in Unity or Arduino would be really appreciated.

Thanks

flexbottle.ino (119 Bytes)