Tablet [Q] Storage showing less

I bought 5 tabs from China to sell in my country. 4 of them got sold with no problem but the 5th one is having problems.
The rest 4 showed 8gb of storage if I checked storage in settings but the 5th one is showing only 2gb. So i downloaded partition table from the play store and found out that mmcblk0 (3707 MB) that is 3.5GB is unmounted. So I want to know how do I mount this? It's urgent. I havea lready sold the tab and I have a few hours to repair this and give it back to the guy who bought it. Please help me.
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