What device, make/model, are you seeing this issue on? I have a Droid Turbo 2 and I cannot duplicate your issue with Message+ v6.6.7. When the 10 I type gets highlighted, I'm not presented with an option to replace it with an emoji. I just keep typing what I want, e.g. pm and 10pm is what stays. I do have 'Enable Smart Emojis' turned ON, if that means anything.
...Just another VZW customer...trying to offer some assistance...