Updated doc: environment-variables.md (#3758)

Added 'defaults to 500' for GRAPH_ETHEREUM_MAX_EVENT_ONLY_RANGE

Author: Jacob273

docs/environment-variables.md

@@ -29,7 +29,7 @@ those.
 - `GRAPH_ETHEREUM_MAX_BLOCK_RANGE_SIZE`: Maximum number of blocks to scan for
   triggers in each request (defaults to 1000).
 - `GRAPH_ETHEREUM_MAX_EVENT_ONLY_RANGE`: Maximum range size for `eth.getLogs`
-  requests that dont filter on contract address, only event signature.
+  requests that dont filter on contract address, only event signature (defaults to 500).
 - `GRAPH_ETHEREUM_JSON_RPC_TIMEOUT`: Timeout for Ethereum JSON-RPC requests.
 - `GRAPH_ETHEREUM_REQUEST_RETRIES`: Number of times to retry JSON-RPC requests
   made against Ethereum. This is used for requests that will not fail the