Performance Monitors / monitors

We need to report when a device has fell behind on firmware, most SNMP records report back as strings. I can see that your defaulted fields correctly convert to numeric so why don't the custom performance monitors do this:

Example:
D-Link DSR1000ac OID - .1.3.6.1.4.1.171.20.3.11.1.4.1.1.4.0
This reports firmware 3.11

But the performance monitor converts this to 3 which is useless
We need this to convert the string properly ie 3.11

Also we have the Billion 8900AX
The firmware comes back as string 2.32e - StringtoNumeric converts to just 3
How can we monitor this. Note, when we just leave it as a string, we never get feedback so what is the point of the contains / not contains fields when they do nothing?