long getOffset(Address address, int ordinal, int size) throws PdbException {
		VirtualBaseTable table = vbtByAddress.get(address);
		if (table == null) {
			throw new PdbException("Virtual Base Table does not exist for address: " + address);
		}
		if (!(table instanceof PdbVirtualBaseTable)) {
			throw new PdbException("Not a PDB Virtual Base Table for address: " + address);
		}
		VirtualBaseTableEntry entry =
			((PdbVirtualBaseTable) table).getOrParseEntryByOrdinal(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
@param size size of a vbt entry offset value
@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/PdbVbtManager.java