ISPadmin multiplies speeds defined in tariff setup by rate_exponent.
You can define the value in Settings System Settings General, ID rate_exponent.

Rate_exponent determines real speed which is given to a client. The default value after the installation is 1.2, so at the speed of 1024 kbit/s, the final speed assigned will be 1228 kbit/s. This increase of tariff speed basically "covers" client´s protocol overhead and potential packet loss, which may occur on WiFi. The client will be satisfied because of higher speed than is actually agreed in the contract. It is not always possible to explain to the client that if they have 1 Mbit/s, there will never be shown 128kB/s during measuring the speed due to the protocol overheads. Thus it is useful to slightly increase the speed of the line and thus reach the desired optical impression.

This "rate exponent" may be used in other cases, too. E.g. for global speed increase for all tariffs in cases of promotional events, or on the contrary to temporarily lower the speed to all clients because of insufficient data transfer efficiency during an unexpected failure or missing connectivity.