First, if you want this to be a single day count, you can do earliest=-0d@d latest=now to count from midnight last night until now. If you want this to be a rolling 24hr count, then you do earliest=-24h@h latest=now and it will calculate 24 hours back anytime you run the search.
Next to tackle the count totals, look into eventstats instead of stats. You'll have to experiment some and look at what eventstats gives you for totals, and dedup on src prior to the count. I don't have the data to try this on, but perhaps something like this:
index=[app] [keyword] earliest=-24h@h latest=now | dedup src | fillnull value=NULL cs5 | eventstats count by src, cs1, cs5 | eval cs5 = case(cs5="NULL","No MSRT Fix",1=1,"MSRT Fix Available")
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