Air Speed vs Ground Speed

I am not a pilot but I have worked hard to practice and advance enough to fly in the advanced server environment. Please pardon my ignorance on the subject but I need some clarification on speed. When ATC requests that I do not exceed XXX kts, are they referring to air speed or ground speed? I know that sounds like a stupid question, but I was just ghosted by Maui approach and I thought I was following all of the instructions exactly, including flight plan, speed, altitude and rate of descent.

The normal speed rule of less than 250 kts below 10,000 is based on air speed, so my assumption was that ATC requests are based on the same measure. However, during the event today I was following the “air” speed requested by ATC of 220 kts and was given a warning “do not exceed 220 kts”. I figured, ok, they must be referring to ground speed, so I lowered my air speed to around 190 kts which put me at just below 220 kts. I then received a “thank you” from ATC. I thought all was well at this point, but about two minutes later I received a “please follow instructions” message and then immediately following that I was ghosted.

I’m just trying to determine what I did wrong so that I can make sure I am following all rules correctly. Any help will be appreciated.

Yes ATC can only see ground speed but they actually give you airspeed requests I don’t think any of them realize this though I don’t know why you were ghosted while complying with ground speed however.

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