Don't worry about it. Volvo installs 90 degree thermostats on all of them now. They don't carry the 87 degree ones anymore. You can of course still buy them aftermarket but all the Genuine Volvo ones are 90.
Just means the engine gets a bit hotter before the thermostat opens up- no big deal. Best if you live in a colder climate as it will allow the heat in the car to be warmer when it comes on (therefore, great for Indiana!).