private JPanel buildMainPanel(Program program) {
		JPanel panel = new JPanel(new PairLayout(10, 5));
		panel.setBorder(BorderFactory.createEmptyBorder(20, 20, 10, 20));
		addrInput = new AddressInput(program, a -> clearStatusText());
		addrInput.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				okCallback();
			}
		});
		addrInput.setAddress(defaultAddress);

		panel.add(new GLabel("Enter Base Address:", SwingConstants.RIGHT));
		panel.add(addrInput);

		comboBox = new GComboBox<>(new String[] { "1", "2", "4", "8" });
		int pointerSize = defaultAddress.getPointerSize();
		comboBox.setSelectedItem(Integer.toString(pointerSize));
		comboBox.getAccessibleContext().setAccessibleName("Address");
		panel.add(new GLabel("Select Data Size (Bytes):", SwingConstants.RIGHT));
		panel.add(comboBox);

		signedCheckBox = new GCheckBox("Signed Data Value(s)", true);
		signedCheckBox.getAccessibleContext().setAccessibleName("Signed Data Value");
		panel.add(signedCheckBox);
		panel.getAccessibleContext().setAccessibleName("Offset Table");
		return panel;
	}
Get the selected size of the data type.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/references/OffsetTableDialog.java