The ecredit can only be used to pay for the airfare part of the Delta vacations package
Here is an example of comparison

Atlanta to Paris (airfare only and booking hotel on your own outside of delta) depart 4/11/2023 and return 4/21/2023
2 adults - main cabin - nonstop flights -$1,608 roundtrip per passenger - or $3216 total for 2 people

Compare to Delta Vacations booking (airfare+hotel package through Delta Vacations) -- depart 4/11/2023 and return 4/21/2023 using in this example a hotel such as Le Dokhan's, A Tribute Portfolio Hotel, Paris--the total for 2 people is about $6,550 for 2 people (the hotel stay would actuallly be check-in 4/12/2023 check-out 4-21-2023 due to flight time leaving Atlanta 4-11-23 and arriving in Paris 4-12-23)
If you used the same flights (nonstop, main cabin) in your Delta Vacations (airfare+hotel package) booking--the "airfare portion" of the Delta Vacations package is only $804 roundtrip per person (or $1,608 total for the 2 people) and your Delta ecredits can be used to pay for the airfare portion of the package - subtract that $1608 "airfare portion" you paid using the Delta ecredits and you still owe $4,942

If you go to the hotel website and try to book those same dates (check-in 4/12/2023 check-out 4-21-2023) in same class of room for those dates it comes out to $4,540 Euros (currently about 4,833.51 USD)