long getOffset(Address address, int ordinal) throws PdbException {
		VirtualBaseTable table = vbtByAddress.get(address);
		if (table == null) {
			table = createVirtualBaseTable(address);
		}
		VirtualBaseTableEntry entry = table.getEntry(ordinal);
		if (entry == null) {
			throw new PdbException(
				"Virtual Base Table Entry does not exist for ordinal: " + ordinal);
		}
		return entry.getOffset();
	}
Returns the offset from the virtual base table entry
@param address Address of virtual base table
@param ordinal index into table
@return the offset
@throws PdbException if no table exists for address or no entry exists for ordinal
Ghidra/Features/PDB/src/main/java/ghidra/app/util/pdb/pdbapplicator/VbtManager.java