TAS

I live in Michigan. I was flying recently and the OAT was -10. Barometric pressure 30.58 and altitude 3000 ft. I have dual Garmin G3x touch screens. The airspeed indicator strip said 148 kts but the TAS at the top of the strip said 143 kts. My earlier flying has always shown the TAS to be higher than the indicator strip. Why the difference the other day?

Flying at a lower density altitude than actual, instead of higher?

So that's how that works.

The actual definition of calibrated airspeed (which is the same as IAS if there are no errors) is your true airspeed, multiplied by the square root of the normalized air density. The normalized air density is the density of the air at your altitude divided by sea level air density on a 'standard day'. So on a cold day, not too high up, the normalized air density can be greater than one.