sp_spaceused reveals 0 rows but 72 KB of reserved space
Likely, there is an IAM page and extent reserved for this table. TRUNCATE TABLE will remove these. When all data is just deleted, a bare minimum structure will still exist for the table.

Have a demo!

--Setup
DROP TABLE IF EXISTS dbo.welcometable
CREATE TABLE dbo.welcometable
(ID INT)

EXEC sp_spaceused 'dbo.welcometable'
--all 0s

-----------------------------------------------------
--Let's see what spaceused looks like when there's data
INSERT dbo.welcometable
VALUES (1)

EXEC sp_spaceused 'dbo.welcometable'
--72KB reserved, 8KB data, 8KB index, 56KB unused

-----------------------------------------------------
--Now what if we delete?
DELETE FROM dbo.welcometable

EXEC sp_spaceused 'dbo.welcometable'
--72KB reserved, 8KB data, 8KB index, 56KB unused

-----------------------------------------------------
--What if we truncate?
TRUNCATE TABLE dbo.welcometable

EXEC sp_spaceused 'dbo.welcometable'
--all 0s
--success!


If you want to actually see the pages and where they are, use this:

SELECT page_type_desc, allocated_page_page_id, is_allocated
FROM sys.dm_db_database_page_allocations(DB_ID(),OBJECT_ID('dbo.welcometable'),NULL,NULL,'DETAILED')


This shows one IAM page and one reserved extent for me, even when all rows have been deleted.