The value in the parenthesis of language expressions signify how many next symbols are needed to make a decision.
For example, without reading a symbol from the input, we cannot decide in LL(1) grammars which rule must be applied for derivation.
In this point, Some thought like that occurs:
we can make a decision without reading a symbol from the input in LR(0) grammars for specific derivation.
However, I do not think like that, because we always need an input character in LR(0) parsers. We decide to apply shift or reduce operation by regarding next input symbol. In this case, why is it regarded as LR(0) ?