Update witness_parameters.md

doc/witness_parameters.md

@@ -1,6 +1,6 @@
 # Witness Parameters
 
-The role of a witness in the Steem Blockchain is verify incoming transactions, produce blocks when scheduled, and partake in the Steem governance model by voting on several parameters.
+The role of a witness in the Steem Blockchain is to verify incoming transactions, produce blocks when scheduled, and partake in the Steem governance model by voting on several parameters.
 
 These parameters control various aspects of the operation of the blockchain that are not easily defined in code at compile time. One example is the STEEM price feed that defines the conversion rate between STEEM and SBD.
 
@@ -45,7 +45,7 @@ A more detailed explanation of resource dynamics can be found [here](./devs/2018
 
 ### maximum_block_size
 
-The maximum size of a single block in bytes. The value must be not less than `65536`.
+The maximum size of a single block in bytes. The value must be not less than `65536`. The value must not be than 2MB (2097152).
 
 ### sbd_interest_rate
 
@@ -62,4 +62,4 @@ A witness published URL, usually to a public seed node they operate, or a post a
 
 ### new_signing_key
 
-Sets the signing key for the witness required to validate produced blocks.
+Sets the signing key for the witness, which is used to sign blocks.