For a better stratification you would have to increase the range of these settings. The buffer will never exceed the maximum temperature profile you define with parameters OVHT-01 to OVHT-05.
The default values of the maximum load level temperatures OVHT-01 to OVHT-05 are set for a low stratification between 78 (maximum lower) and 90 maximum upper) temperatures.
For e.g. under floor heating you have to change the maximum temperatures to OVHT-03 = 45…50 °C, if the under floor heating circuits are supplied form the middle level of the buffer.