That's because the IMG file only has the image of a 32GB microSD card. When you use ApplePi Baker to burn a new card, it remains 32GB, no matter what the physical card size is.
If you had stuck with the Samsung card, you could have lived with 32GB. Many of the budget cards are not as large as 32GB (they round up), so you can't burn the ASIAIR IMG into them.
If you can access Linux ext4 format, you can repartition to recover the entire 64 GB; but it is better to use a USB drive (USB stick or SSD) for storing images, if you need more space (or even if you don't).
Don't sell yourself short with the budget cards. It is not like the Samsung cards are especially expensive either:
https://www.amazon.com/gp/product/B07NP96DX5
Chen