32 gigabytes = 29.802 gibibytes
Your SD is 29.802 GiB in capacity, not 32 GiB.
I'm not sure about the other 1 GiB, but it happens.
The filesystem could possibly be reserving some of that space, accounting for the 1 GiB difference . Either way, there's nothing wrong with the SD at all.
Also, howtogeek explains this perfectly.