Tomb
A chart describes tendencies in a traditional system. It cannot decide health, money, law, marriage or children.
In the classical sources
十二曰墓，又曰库，以万物成功而藏之库，如人之终而归墓也
Twelfth is Tomb, also called Storehouse: things that have done their work are put away in store, as a person at the end returns to the grave.
三命通會 卷二
About this stage
墓 is the grave and its alternate name 库 is a storehouse, and the simile keeps both meanings in play. 三命提要 places it last of the twelve, just before the breath returns. The four earth branches take the tombs of all ten stems in the table used here, with 未 for 甲, 戌 for 丙, 丑 for 庚 and 辰 for 壬.
五行大義, which calls the stage 葬, burial, turns it into a small domestic puzzle about earth. Earth could not share 戌 with its mother fire or 丑 with its child metal, and dared not enter 未, the grave of wood, so it goes to 辰 and lies with its wife, water. The book backs this with a line from the Book of Songs about sharing one grave. 神峰通考 prefers the word 库 in its tables, and that storehouse sense keeps the position from being only an ending.
Where this text comes from
The order of the twelve stages follows 五行大義 volume 2 and 三命通會 volume 2 on Wikisource. The calculator uses that order for wood, fire, metal and water. Works disagree about earth.
The English name follows common modern usage. The wording here is our own plain summary.