"value: the value to write, from 0 to 255 (byte)"

and

"A byte stores an 8-bit unsigned number, from 0 to 255."

So, no decimals allowed. Looks like you need to split your number into 2 parts, the whole part and decimal part. Multiply the decimal part by 10, store the two resulting integers and do the reverse when you read them back. There may well be a library to do this that hides the mechanics of how it works. As I have never used the Arduino EEPROM I don't know if there is a better way.