use BigIntegerField for a hugher range ;-)

InvenTree/order/migrations/0054_auto_20211201_2139.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.2.5 on 2021-12-01 21:39
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('order', '0053_auto_20211128_0151'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='purchaseorder',
+            name='reference_int',
+            field=models.BigIntegerField(default=0),
+        ),
+        migrations.AlterField(
+            model_name='salesorder',
+            name='reference_int',
+            field=models.BigIntegerField(default=0),
+        ),
+    ]