The September 8, 2022 edition of the Aeronautical Chart User’s Guide notes that:
Beginning with the September 8, 2022, publication date, all Standard Service Volume designations will be shown for VOR, VOR/DME, VORTAC, DME, and TACAN NAVAIDs on both the IFR Enroute Low and High Attitude charts.
Publishing this information is part of the FAA plan to implement the Minimum Operational Network (MON) of VORs (see also AIM 1-1-3-f), which will leave some 589 VORs still in operation after the program is complete, now scheduled in FY2030.
As the FAA decommissions VORs, mostly in the East and Midwest, it is expanding the service volumes of the navaids to help ensure signal coverage for aircraft not equipped with GPS or during GPS outages. The table below, from the Aeronautical Chart User’s Guide, shows both the new service volumes and the codes used on IFR charts to identify the service volume associated with each VOR.
Here’s a section of a low-altitude IFR chart that shows navaid information boxes with some of the new standard service volume classifications.
You can find more information about the new VOR service volumes in AIM 1−1−8. NAVAID Service Volumes.
BruceAir, LLC 
I’ve read through the Aeronautical Chart Users’ Guide and the AIM 1-1-8, admittedly hurriedly. So maybe I just skipped over it. I have yet to see anything in print that says what the first service volume and second service volume in the VOR information boxes are referring to. I found one example of (VH)(H). Since VH is the new VOR svc volume, I’m guessing that the second designator is always the DME svc volume while the first service volume is always the VOR. Is that a correct guess?
It also says that TACAN will retain the original service volume. So, with a VORTAC information box with (H)(H), what is the TACAN, VOR, and DME service volumes?
Thanks
You may find it helpful to review the progress of the change at the Aeronautical Charting Meeting. It was described and discussed in #21-02-365 (PDF): https://www.faa.gov/air_traffic/flight_info/aeronav/acf/media/RDs/21-02-365_Add_SSV_Classifications_to_IFR_Low_Altitude_Enroute_Charts.pdf
Thanks