You are correct, that is the filter.
Do you try resetting the indicator and then drive the engine and see where where the level is? Also, did you look at the indicator when the coach was first purchased new at the dealers or soon after to see where it was indicating. Some of the GS coaches read high even when the filter is new due to some restriction on the intake.
If I remember correctly mine reads around 16 all the time. Our coach is in the storage lot and not at the home so I can't check right now. On our previous coach I had over 22k on it and on our present have 8k and never had to change the filter on either one.
But CAT recommends not changing the filter until it is almost in the "red" on the indicator. Also, I talked to a Fleightliner rep and he said the indicators were not an accurate indication of filter condition. He stated to look at the indicator where it read when filter was new and most of the time they read high when new depending on duct work restriction.
At 5k the filter should not be dirty or need changed. I have 8k on ours it still reads the same as when we picked it up at the dealers when new.
There is a post here about a 2006 Tour Master Air Intake and it having a clogged filter at 5k. You might want to look at it.
Ron