1. Split gif attachments into frames.
2. Merge them in Photoshop.
3. Add contrast using levels.
4. Add some gaussian blur.
5. Add more contrast using levels.
6. Invert image.
7. Redraw QR in google sheets or excel. We need to add a position block at top left, duplicate format info (error correction level, mask pattern, format error correction), add alignment block, and add timing blocks.
8. Read QR, which leads us to click me!
9. Decode the following link from base64 to png image.
10. Use the following site to see that the first numbers '7' and '8' in phone and watch rows were modified.
11. Calculate the amount once again.
12. Trying to recalculate again and again, because the task was bugged, and one of the flags worked, we're not sure which exactly. Most probably it is the one listed lower.

Flag: VishwaCTF{573843}.