OK, apart from being vertically challenged, also mathematically challenged!
Reply from Hermys reference thermostats;
Thank you, you need T2100715. When I type your VIN into my system it just gives me the one that you need but according to Triumph it is cutoff with the engine numbers below. The engine number and VIN number are normally close.
T2100715 Thermostat $55.59 1 > Eng No 616640
1 T2100891 Thermostat $48.25 Eng No 616641 >