Hi Mark,
The Modbus read data tool in Mango displays the register result in hexadecimal, so 0x37 is 55. Might the value have changed between the readings? You can use the point locator test tool if you want to decode the register by describing the type of data in the register. Another part of the mystery is that Mango begins its addressing at 0, where associating the values in 1025 and 1026 may suggest modscan uses a base address of 1.
Edit: Also, I find it strange you say Modbus RTU when the screenshot from Mango is of an IP data source.