That's because the type of minp1 and maxp1 are still floats, you can change them to ints by passing them to the int(..) constructor:
minp = 23.75
maxp = 192.4
minp1 = int(round(minp, 0))
maxp1 = int(round(maxp, 0))
print("Size between " + str(minp1) + " to " + str(maxp1) + ".")
Or in a terminal:
$ python3
Python 3.5.2 (default, Nov 17 2016, 17:05:23)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> minp = 23.75
>>> maxp = 192.4
>>> minp1 = int(round(minp, 0))
>>> maxp1 = int(round(maxp, 0))
>>> print("Size between " + str(minp1) + " to " + str(maxp1) + ".")
Size between 24 to 192.
Nevertheless, it is not a good idea to do string processing/concatenations yourself. You better format it with a formatting string, like:
minp = 23.75
maxp = 192.4
minp1 = round(minp, 0)
maxp1 = round(maxp, 0)
print("Size between %d to %d."%(minp1,maxp1))
Here %d stands for "Signed integer decimal". So by using format, Python will fill in the variables at the %d places itself which is elegant and requires less thinking from your side.
, 0part:round(minp).