It is 4R photo size! (not R4)

Dimension for 4R photo: 4" x 6" (101.6mm x 152.4mm)
Dimension for 5R photo: 5" x 7" (127mm x 177.8mm)
Dimension for 8R photo: 8" x 10" (203.2mm x 254mm)

incorrect! Dimension for 4R photo (3:4)

• 480px X 640px
• 1024px X 768px
• 1200px X 1600px
• 3072px X 2304px