NLT - 23 “Then make a table of acacia wood, 36 inches long, 18 inches wide, and 27 inches high.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
✿ Fourfold reasons for God giving exact measurements and specific instructions to build Table of Showbread in the Bible:
1. Since the tabernacle was God's dwelling place in Israel
2. It typified God's real and eternal dwelling place now and for ever
3. The ark, altar of incense, and table of showbread, candlestick and mercy seat are symbolic of Tabernacle in Heaven
4. All the shittim wood of the tabernacle was covered with gold fitting the New Jerusalem which is made of pure gold (Rev. 21:18,21)
✿ Eighteen Specific Commands to build the Table of Showbread:
1. Make a table of shittim wood (Ex. 25:23).
2. Length: 4 ft. 2 inches
3. Breadth: 25 inches
4. Height: 37 1/2 inches
5. Overlay it with pure gold (Ex. 25:24).
6. Make a crown of gold around it.
7. Make a border of about 4 inches around the table (Ex. 25:25).
8. Make a golden crown to the border.
9. Make four rings of gold (Ex. 25:26).
10. Make four legs for the table.
11. Put the four rings in the four corners of the legs against the border for staves to carry the table (Ex. 25:26-27).
12. Make two staves of shittim wood (Ex. 25:28).
13. Overlay them with gold.
14. Make dishes and spoons for the table (Ex. 25:29).
15. Make covers for the dishes.
16. Make bowls for the table.
17. Make them of pure gold.
18. Set showbread on the table before Me always (Ex. 25:30).
I don't know why the measurements for this table referred to in the question needs to be the size that it needs to be, but there are some things we can consider about this "table."
As for why God gave specific instructions for its construction, I would be really surprised if God told them to build some things FOR HIM if He didn't get real particular about it.
What's the function of a table? This one is exactly twice as long as it is wide, (36" 18"). A table is where food is consumed; it's where we have our meals, get our nourishment. This one was where the "show bread" would be. What does the "show bread" signify or represent?
These are the things we can consider that might help us to theorize (that's all we can do is form theories) why the bible wants us to know the specifics of the table. We need to remember that all of scripture refers to Jesus in one way or another.