Supported symbols is <
{% if TestValue < '5' %}Is Less Than 5{% else %}Is Greater Than Or Equal To 5{% endif %}
Supported symbols is <=
{% if TestValue <= '5' %}Is Less Than Or Equal To 5{% else %}Is Greater Than 5{% endif %}
If the input value is not an integer, this will NOT error, but will evaluate as false
So, given the above examples, if the value is Not-A-Number then then else condition will output/execute
If the value being checked is an integer (for example if you have used the length filter) then the conditional value should also be an integer.
{% if PropertyGroup|length < 1 %}No Instances Of Group{% else %}At Least 1 Instance Of Group{% endif %}