Intro: How to Fix Sd Card Low Capacity
First you have to download sd card formatter (here is a link: https://www.sdcard.org/downloads/formatter_4/)
Then install it
Step 1: Step 2 : Format Sd Card
Open SDFormatter V4.0. then select drive and click options.
Finally select from FORMAT TYPE, FULL (Erase) and click format.
Your sd card should be original size agan.