STMicroelectronics M4T28-BR12SH1 part marking

What do the numbers on the STMicroelectronics part M4T28-BR12SH1 call out?

991LN = Internal to supplier
M4T28-BR12SH1 = Part Number
Timekeeper®
Snaphat®
CONTAINS LITHIUM CELL
MYS 99 805 = aaa bb YWW = The aaa and bb are internal, YWW (Year, Work Week)

Source- Solved: M4T28-BR12SH1 - meaning of package markings? - STMicroelectronics Community