Tag Eng High and Low reset when import

We are using Ignition version 8.1.13 for our project. Yesterday we exported tags from Ignition tags and imported at local gateway (which have same GWBK restored day before yesterday). We had changed priorities of some alarms (x200) and imported back to Site GW. While importing we have used OVERWIRTE option.
After import we found that the Eng. High and Low changed to default 0-100.
Please advise, if there is any issue/bug in the Ignition tag import or it is normal. So next time we will be aware of this type of issue.