I have recently purchased an 05, model 5203 and have a question. The owners manual says the 540 PTO speed is achieved @ 2400rpm. There is a PTO symbol on the tach showing that. However there is another PTO symbol at 1700 rpm. This symbol has an 'E' under it. Does anyone know what this 'E' represents? The engine is much quieter when running at the 1700rpm and that is what I have been using when bush hogging unless in heavier material. Thanks