Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Symbol | GSI | Meaning | Unicode | Description |
| --- | --- | --- | --- | --- |
| ◬ | ○ | Base triangulation surveying point | U+25EC | Dot in upward-pointing triangle |
|  | ○ | Electronic triangulation point |  | Dot in upward-pointing triangle with flag |
| ⊡ | ○ | Benchmark | U+22A1 | Dot in square |
| ⛭ | ○ | Factory | U+26ED | Gear without hub |
| ⛯ | ○ | Lighthouse | U+26EF | Map symbol for lighthouse |
| ⛮ | ○ | Power station | U+26EE | Gear with handles |
| 文 | ○ | Elementary or junior high school | U+6587 | Kanji bun |
| ㉆ | ○ | High school |  | Kanji bun in a circle |
|  | ○ | University |  | Kanji bun with a smaller kanji 大 (for daigaku) in brackets on top |
|  | ○ | Technical college |  | Kanji bun with a smaller kanji 専 (for senmon gakkō) in brackets on top |
| 〶 | ○ | Post office | U+3036 | Down tack (T-shape) with overbar in circle |
| 〒 | × | Sub post office (not distribution centre) | U+3012 | Down tack (T-shape) with overbar |
| ⭙ | ○ | Police station | U+2B59 | Heavy circled saltire |
| ☓ | ○ | Koban (police box) | U+2613 | Diagonal cross (saltire) |
| ⊕ | ○ | Public health centre | U+2295 | Greek cross in circle |
| ⛨ | ○ | Hospital |  | Greek cross in shield |
| ⭖ | ○ | Prefectural Office | U+26FB | Oval bullseye |
| ⭗ | ○ | City hall | U+2B57 | Heavy circle with circle inside |
| ◉ | ○ | Ward office | U+25C9 | Fisheye |
| ⭘ | ○ | Town hall | U+2B58 | Heavy circle |
| ⛩ | ○ | Shinto shrine | U+26E9 | Shinto shrine |
| 卍 | ○ | Buddhist temple | U+534D | Manji (Swastika) |
| ⛫ | ○ | Castle | U+26EB | Castle |
| ⛼ | ○ | Cemetery | U+26FC | Headstone graveyard symbol |
| ♨ | ○ | Onsen (hot springs) | U+2668 | Oval with three vertical wavy lines |
| ⛬ | ○ | Historical landmark | U+26EC | Historic site |
| ⛰ | ○ | Summit | U+26F0 | Mountain |
Question:
how many symbols are not shown?
Answer:
3