There are many variations for describing the Property Length. For example:

943 The length of the Properties in the CONNECT Packet variable header encoded as a Variable Byte
944 Integer.

1342 The Property Length in the CONNACK Packet variable header encoded as a Variable Byte integer.

1697 The length of the Properties in the PUBLISH Packet variable header encoded as a Variable Byte integer
1698 followed by the Properties.

1957 The length of the Properties in the PUBACK Packet variable header encoded as a Variable Byte integer.
1958 If the Remaining Length is less than 4 there is no Property Length and the value of 0 is used.

2011 The length of Identifier/Value pairs in the PUBREC Packet variable header encoded as a Variable Byte
2012 integer. If the Remaining Length is less than 4 there are no Length of Identifier/Value pairs and the value
2013 of 0 is used.