This question is more related to culture rather than language. Normally used measures are as following:
- 茶さじ according to various sources varies from 2.5 cc to 6cc so it is quite unreliable measure.
- 小さじ is 5cc
- 大さじ is 15cc which equals to about 6 grams of tea.
- カップ is 200cc
Regarding the amount used for this particular tea I would guess this is not green tea but kind of 麦茶 or, possibly, ほうじ茶 for which using larger amounts is common. "normal" green tea will be too saturated if used in such amounts.
Some reference found on internet: measures and weights
