You have 900 or so views with 19 subs. That's not a huge discrepancy. A lot of those are one person who looked at all your pages, so 19 subs is a good number.
Keep in mind that some of those 900 views is the same person coming to read again. The counter ticks with every chapter they read, so if one person goes through several chapters, the view counter will counter will tick multiple views.
Another thing to remember is that not everyone who reads has a Tapas account. They might simply bookmark your comic.
And lastly, considering that Tapas hides the subscribe button on the desktop version of the site, subs are not very high.