When I am at or higher than 10000 feet set in atiltude, ATC wants me to slow down to 250kts or slower.   It varies but also always does that at 10000 feet.  Once I am at 18000 it never does that anymore.   This has been this way for a while, but I thought I would just bring it up

Where are you flying when this happens, is there a speed / altitude restriction on the charts for this area?

There is also a setting to ignore some of these restrictions.

ATC Ignores Published Speed Limits – This option will stop ATC from directing you to slow to the speeds published in the SID, STAR or Approach procedures you’re flying. NOTE: Aircraft designated as “HEAVY” in the call sign will be given leeway to exceed the published speeds for safety reasons.

ATC Ignores Below 10000 Ft Speed Limit – There’s a pretty much universal ATC rule to fly at 250 knots or less when under 10,000 feet MSL. If you want to fly a low level bombing run at 500 knots – or just don’t want to be nagged about your speed – check this option. NOTE: Aircraft designated as “HEAVY” in the call sign will be given leeway to exceed the 250 knots speed limit for safety reasons.