Numbers on props

[DrizzyDrones]

Ok so i was gonna do a prop swap because when the cat batted it even with no apparent dmg or app warning it is better to just swap the props now non fly more combo has only extra props for two engines I understand the marking and where to install them but im wondering what the numbers like front left (when drone facing away from you and rear are closest) has numbers D1 4726 F on the front right its B2 4726 F ... on the left rear F1 4726 F and right rear is E2 4726 F what do they mean my spare props have E3 and I3

 

[bumper]

Injection molding machines for small parts often have numerous cavities. If there's a QC problem in the finished product, it's helpful to know which cavity is suspect, so the cavities will often have individual numbers/letters for ID purposes.